Audi RS6 Performance vs S8 Plus test drive: Extrovert or Introvert?

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These two Audis share the same massively powerful engine, but go about their business in wholly different ways. So which should you have: the bonkers RS6 Performance, or the discreet S8 Plus?

Power comes in many different forms, and nowhere is this more aptly played out than in the automotive game.

In an era when even hot hatchbacks have outputs that are knocking on the door of 400hp, there should be something out there to suit the taste of every performance car fan – whether they prefer in-your-face styling and loud, shouty exhausts, or discreet bodywork hiding a powerplant that could flatten cities should it feel like it.

Happily, premium manufacturer Audi provides two cars that are the very crystallisation of this theory. Both the cars you see in the picture here feature an identical drivetrain: namely, a fearsomely potent 4.0-litre biturbo V8 petrol, driving all four wheels through an eight-speed Titronic automatic transmission.

Yet they couldn’t be more different in their character or appearance, so which one is – for want of a better word – best?

Lining up as the steroidal pugilist of the pair is the RS6 Avant Performance. Based on what Audi internally terms the ‘C7’ fourth-generation A6, the regular £79,505 RS6 has plenty enough grunt for most needs, given it has the 560hp/700Nm iteration of this 4.0 V8 – meaning it is capable of 0-62mph in 3.9 seconds.

However, as the C7 was launched in 2011, it is getting on a bit in car years now and is due for imminent replacement, probably sometime late in 2017.

That meant Audi felt it could give the RS6 a final shot-in-the-arm hurrah, bestowing upon it the epithet ‘Performance’ to signify a power output of a colossal 605hp – with up to 750Nm backing it up on a time-limited overboost phase – that sees the 0-62mph time cut by two-tenths to 3.7 seconds.

That’s blistering acceleration for any motor, never mind something that could haul a couple of Labradors about in its rear section.

Little has changed externally or internally for the Performance compared to a, ahem, boggo RS6, although you might spot this special version courtesy of its slightly different bumper/air intake arrangement at the front and those glorious, gorgeous 21-inch wheels, which are of a bespoke design for the Performance.

There is a special colour for it too, called Ascari Blue, but KP16 VWE is finished in the equally lovely Sepang Blue.

The premium for the extra 45hp and brief burst of an additional 50Nm? A hefty £5,580, as the Performance starts at £85,085… although this particular car totalled an eye-popping £102,755, thanks in chief to £9,375 on the optional carbon ceramic brakes, £2,100 on the Assistance Pack of driver aids, £1,300 on a panoramic sunroof and another £1,000 on RS Sport suspension with Dynamic Ride Control, plus a few sundry other additions.

Whether you think six figures for what is essentially an Audi A6 underneath it all is good value or not doesn’t really come into it, as the RS6 has a desirability factor somewhere in the stratosphere – we’ll come back to this point later.

Lined up next to the bristling wheel arches and quattro-emblazoned nose of the RS6 Performance, the S8 Plus looks almost lost, especially as KX66 RVA is finished in sedate Daytona Grey.

S-model Audis are nothing like as aggressive as the RS models but as Audi doesn’t deem an RS8 necessary (BMW doesn’t do an M7, for instance, although the Mercedes-AMG S63 and Jaguar XJR are both focused, high-performance large executives), then the S8 forms the range-topper. Based on the third-generation ‘D4’ A8, this is an even older car than the A6, as it was launched in 2010 and so will definitely be replaced by an all-new example early in 2017.

The A8’s trick, ever since it first appeared in 1994, is that it is mainly made of aluminium to keep the weight down, but even so the S8 is incredibly 40kg heavier than the RS6 Performance, which means the Plus is ever-so-slightly slower to 62mph from rest – 3.8 seconds, though, is still alarmingly quick for a big four-door machine.

The thing is, there’s a lot to be said for the Q car and if ever there was a blinding Q car, the S8 Plus is it. To look at, it might as well be an A8 TDI – sombre, little hint of what power it possesses (quad exhausts and subtle ‘S8’ badging notwithstanding), none of the showmanship of the RS6. Indeed, there’s nothing really to mark out the Plus, save for lots of black detailing in place of the silver-effect door mirrors, window surrounds and grille frame you’d get on the regular version.

Talking of which, Plus treatment adds more horsepower to the regular £82,075 S8, as that car comes with 520hp as standard, so it’s an 85hp hike here as opposed to 45hp on the RS6. But then the premium is more too – Audi asks a colossal £14,750 for the Plus over and above the S8, while options once more pushed our car’s ticket to a scary £200 shy of £112,000.

Chief extras here were £5,565 on the Bang & Olufsen Advanced Sound System, £1,635 for cooled and massaging front seats, £1,535 for Night Vision Assistant with pedestrian and animal detection, £1,340 on the head-up display and £1,100 for deluxe four-zone climate control, among more. If you know anything about the depreciation cars like the A8/S8 suffer, you’ll know £111,800 is a heck of a lot to splash out as a result…

So, with the sober S8 offering less practicality as it’s only a saloon while the RS6 is an Avant (estate), costing more to run thanks to being one VED band higher than the RS6, and being more expensive to purchase/finance to boot, it’s starting to look like the RS6 Performance is going to walk this fight. And, returning to the matter of the car’s desirability, if we took a straw poll of people on the street, it would seem they agree with that prediction of the outcome.

During a week with the RS6, we couldn’t park it up anywhere without someone offering hugely positive comments on it, while driving around on dual carriageways and motorways often saw the Performance being tailed by a phalanx of A3s, tuned old A4s, A5 TDIs and Q3s; it’s like the RS6 is the Pied Piper of Audis, ‘lesser’ versions all clamouring behind it to get a brief look at their king.

We heartily approve of its exterior aesthetic. It’s so bullish and those alloys are so drool-inducing, while the blue paint serves its lines beautifully.

The interior is also absolutely cracking, the sculpted, Alcantara-and-leather, honeycomb-branded sports seats and chunky steering wheel being real highlights, although it’s worth pointing out that this generation of A6 cannot be fitted with Audi’s latest Virtual Cockpit arrangement, so its analogue dials and MMI screen that pops up out of the dash are features that won’t appear on the forthcoming new model.

Nevertheless, the interior works wonderfully well and looks beautiful, and it’s properly capacious in there, big enough for five adults and possessed of a giant 565-litre boot at the back. And this comfortable vibe is maintained once you get the RS6 moving.

With its dynamic dampers in Comfort mode, this is easily the best-riding RS6 that has yet been built. There’s none of the typical Audi performance car sharpness about the way it smothers the lumps and bumps, while – because the Tiptronic is a genuine, torque-converter automatic – the gearbox is seamless in operation.

The RS6 never quite lets you forget what it’s all about, however, as the exhausts burble and mutter menacingly to themselves even on part-throttle openings in Comfort mode, while there’s an underlying firmness to the body control that speaks of well-sorted suspension.

Yet it’s entirely conceivable to believe you could, if you had a shedload of cash, live with the RS6 Performance on a daily basis. Crikey, it even returned 28.3mpg on a 128-mile motorway run back from Heathrow airport, which (for a car with 605hp, remember) is incredible stuff.

So it works if you assess it as an Audi Avant. Knock it into Dynamic mode, though, and all holy hell breaks loose. Two tonnes of estate car has no earthly right to move in such a frighteningly rapid and composed fashion.

The RS6 is a brutal, remorseless demolisher of roads. It doesn’t care whether you’re pointing it at a sinuous and bumpy country lane sluiced with mud, a big open A-road with good sighting or a long, clear stretch of the A46 late at night with no one else around; if you depress the throttle anything like beyond halfway, you simply cling on to the wheel and watch in slack-jawed amazement as the Audi roars into what was previously the middle-distance with disarming disdain.

A failing of previous Audi RS6s (there have been two models prior to this one) is that, for all their bombastic pace, they’ve never been exciting to drive. Frequently spoiled by one or all of understeer, a crashy ride and numb steering, they’re cars to be respected but not admired.

This RS6, though, this one’s different. The nine-grand brakes are predictably mammoth in performance, the steering is a delight, beautifully weighted and even feelsome, while the sensation of the RS6’s nose washing wide never, ever once makes itself known.

Sure, the Audi’s party piece is still phenomenal 4WD grip, meaning even modestly talented drivers should be able to get searing pace out of it, but there is a feeling that if you really enjoy motoring and understand what makes for great chassis dynamics, the RS6 will reward a select few who really know what they’re doing behind the wheel.

Oh, and the noise? The noise is sublime. In sportier modes, the exhausts make an obscenely naughty racket all of the time, while the big V8 up front overlays everything with its booming tenor voice. It really didn’t need such augmentation, but the Performance’s soundtrack makes it sound even quicker than it really is.

In total, we spent 12 hours behind the RS6’s wheel, covering 432 miles at 20.4mpg and 35mph averages in the process – and every single minute and mile of them was an event. The RS6 Performance is, by any rational stretch of the imagination, a phenomenal, phenomenal car.

Which makes the S8’s job even harder. And before you’ve driven the thing ten yards, you can tell it’s not going to match the vivacity of the RS6.

The engine is much more muted, while any pops and crackles from the exhaust sound more like artillery fire in distant hills than fireworks in your immediate vicinity. Also, the steering is much, much less pleasant, as it’s too light and inconsistent in its weighting, so you don’t feel as confident bunging the big S8 into the corners as you do in the RS6.

The S8 also has a dashboard layout that’s unlike even its contemporary Audi stablemates, never mind current models, with an unusual sloped centre panel running down to the transmission tunnel and a strange gearshift lever that isn’t as easy to use as the item in the RS6.

Again, the fit and finish cannot be criticised, but by the company’s own high standards for interiors, this is starting to feel dated.

There is some theatre involved, though, such as the MMI screen popping out of its hiding place in the dash, an analogue clock in the console (now seen as a premium touch, despite carmakers spending years phasing such things out for digital displays), the Bang & Olufsen ‘mushroom’ tweeters rising up near the windscreen when you start the car, or the three LED light strips in the roof that suffuse the cabin with a gentle glow at night.

And yet… for all our minor nit-picking of the S8 Plus, we find ourselves adoring it nonetheless. There’s something utterly unhinged about the way this ‘normal’ Audi suddenly goes demented when you mash the pedal into the floor.

It also, with a little less weight over the rear axle, squirms its back end sidewards coming out of junctions with heavy throttle; an oversteering Audi A8?! Whoever would have conceived of such a thing?

There’s also no doubt that the Plus is rabidly quick, despite the backing track not getting much louder even if you knock the car into Sport on the gearbox or Dynamic mode on the MMI (there’s no Drive Select button on the S8, as there is in other hot Audis).

It piles on pace with gleeful abandon, the torque hitting in a rich, relentless surge of shove and muffled V8 bellow. And as it has an even more sumptuous ride than the RS6, then it feels more of a fluid car to pilot – either quickly or more sedately – on a rural road. Honestly, if the steering from the RS6 was ported over into the S8 Plus, we would genuinely have had more fun barrelling the saloon along our favourite roads than the Avant.

That’s a remarkable conclusion to come to, we’re sure you’ll agree, given the RS6’s exalted level of dynamic performance.

In an ideal world, we’d love to have both of them in our dream garage, but this isn’t the ideal world and we have to pick a winner. In the main, it’s the RS6 Performance. It’s cheaper, both to buy and then to run. It’s has it wrapped up for practicality. It’s more involving to drive. It sounds better. It’s faster. It has devastatingly good looks and the more intuitive interior layout.

It’s surely the winner when the scores are totted up, especially as this correspondent has a young child and two dogs, so owning an S8 would be out of the question even if the Lotto numbers actually did come up…

But – like a badly mauled boxer who’s on the ropes, only to deliver a counterpunch knockout blow – there’s something about the S8. More of a mystique. More of a rarity factor.

More of the impression that if the RS6 is the London gangland hardman, all bulky frame in a sheepskin coat, shouting and swearing and offering dire threats of physical violence, then the S8 is the soft-talking professional hitman in an exquisitely tailored suit, silenced pistol hiding in an immaculately lined inside pocket.

First acquaintance with its plain bodywork makes its subsequent sensational performance all the more shocking, somehow, and there’s a real appeal to having something that can easily waste most supercars and yet no one even gives it a second glance. Including the Audi cognoscenti, who clearly know an RS6 when they see one.

So yes, as these are two completely marvellous fast Audis, we yearn for an RS6 Performance. But our perverse nature means we desire an S8 Plus even more.

And, happily, once a few years have passed, it’ll be the saloon that’s by far the cheaper to buy of these two cars. What a monstrous bargain the unassuming S8 Plus will one day be.

TECH SPEC

Model: Audi RS6 Avant Performance
Price: RS6 Performance from £85,085; car as tested £102,755
Drivetrain: 4.0-litre twin-turbo V8 petrol, eight-speed Tiptronic automatic, quattro four-wheel drive
Economy: 29.4mpg
CO2 emissions: 223g/km – £650 VED year one, £295 annually thereafter (if registered before VED laws change on April 1, 2017); 37 per cent benefit in kind
Top speed: 155mph (limited; option to raise to either 174- or 189mph)
0-62mph: 3.7 seconds
Power: 605hp at 6,100-6,800rpm
Torque: 700Nm at 1,750-6,000rpm; 750Nm on overboost at 2,500-5,500rpm

TECH SPEC

Model: Audi S8 Plus
Price: S8 Plus from £96,825; car as tested £111,800
Drivetrain: 4.0-litre twin-turbo V8 petrol, eight-speed Tiptronic automatic, quattro four-wheel drive
Economy: 28.2mpg
CO2 emissions: 231g/km – £885 VED year one, £500 annually thereafter (if registered before VED laws change on April 1, 2017); 37 per cent benefit in kind
Top speed: 155mph (limited; option to raise to 189mph)
0-62mph: 3.8 seconds
Power: 605hp at 6,100-6,800rpm
Torque: 700Nm at 1,750-6,000rpm; 750Nm on overboost at 2,500-5,500rpm