The Big Three’s D-segment sluggers are straining at their leashes, but which dog possesses the most fight?

When the Mercedes-AMG C43 narrowly pipped the new Audi S5 in 2017, we felt that the Ingolstadt car’s subtlety blunted the driver-engaging edge that lent the Stuttgarter a broader overall appeal. And, while the S5 sloped off to lick its admittedly minor wounds, we were waiting with bated breath for the RS5 to enter the fray and exact some revenge on Mercedes-AMG. Understandably, the Affalterbach firm’s riposte would be a snarling, muscle-bound brute and the C63 S Coupé fits that bill to a T.

Not content to retire to its lair and bare its teeth, BMW’s recently facelifted Competition Pack-equipped M4 has also joined the fray. Are the RS5’s rivals all bark and no bite, or will this dogfight turn exceptionally nasty?

Baring teeth

When it comes to decorating its RS models, Audi is about subtlety rather than studded collars. There’s just the slightest flex of muscle to the restrained venting on the snout and sill extensions and a pair of sizable oval tailpipes. Perhaps the biggest clue is this particular car’s 20-inch rims with trapezoidal blades shod with 30-profile rubber.

There will be those who appreciate Audi’s Q-car approach to the RS5 but, when viewed alongside its rivals, it does seem to melt into the background. The C63 and M4 are possessed of more muscular haunches, pronounced wheelarches and power domes adorning their bonnets. It could be argued that the RS5’s handsome deep-blue metallic paintwork tends to absorb the go-faster details, but even if adventurous hues were chosen, there’s not a vast amount separating it from its lesser-powered stablemate, the S5.

Where the Audi does claw back some points is in the cabin. The interior’s ambience echoes the exterior’s subtlety and, short of a fatter, flat-bottomed steering wheel, a light smattering of RS decals and some neat aluminium trim, it’s what you’d largely expect from Audi: amply slush-moulded and solidly assembled.The RS5 also features the most comfortable seats here, providing just enough lateral support and cushioning to cover both cruising and full-attack driving attitudes.

Aud RS5 Coupé vs. BMW M4 Competition Pack vs. Mercedes-AMG C63 S Coupé
The same cannot be said of this C63’s optional AMG Performance pews (R37 300). They do hold you firmly in place, but if you’re even a smidge broader in the beam than average folks, you’ll find the less gym-toned parts of your person flowing unflatteringly over those stiff bolsters; best to stick to the standard seats.

The main gripe levelled at the C63’s interior is its questionable perceived quality. Current-generation C-Class cabins, notably their facias, show a tendency to creak and buzz – we haven’t yet tested one that hasn’t – and that’s something that was especially apparent in the stiffly sprung C63.

The M4 sits squarely in the middle, its materials not being quite as upmarket as those of the RS5, but its assembly being palpably better than that of the C63. Similarly, the seats also provide sufficient lateral hold but, although not quite as cossetting as the RS5’s, are forgiving enough in most instances.

Bark and bite

Audi’s naturally aspirated 4,2-litre V8 ranks right up there as one of the most loved and revered engines we’ve had the fortune of sampling. So it was with mixed emotions that we saw this wonderful powerplant bow out in favour of an all-new 2,9-litre twin-turbo V6 that it shares with the latest Porsche Panamera. It’s an understandable move, especially given the pressures of fuel economy and tightening emissions legislation, but it’s difficult to digest the fact that this unit doesn’t improve on the V8’s 331 kW peak output, although going the forced-induction route does bump the torque up from 430 to 600 N.m. This, along with limpet-grip AWD and a kerb weight roughly 70 kg lighter than the previous car, lends the new RS5 a wicked turn of pace out of the blocks.

In the starkest display of AWD versus RWD in a straight line, we pitted the RS5 against the C63 S in a drag race at Cape Town’s Killarney Raceway. Granted, we knew that Audi, with its propensity for mechanical consistency, would have again wheeled out another Bauhaus bullet, but given the C63’s formidable powerplant – lending it advantages to the tune of 34 kW and 100 N.m – there was, on paper at least, the makings of a potentially close contest. But, such hopes quickly vanished in a pall of tyre smoke from the C63 as it haplessly bucked, slipped and shimmied off the line.

Aud RS5 Coupé vs. BMW M4 Competition Pack vs. Mercedes-AMG C63 S Coupé
In the other lane, the RS5 simply hunkered down, buried its claws into the tarmac and catapulted into action, leaving the C63 floundering in its wake. The AMG simply cannot put the grunt served up by that gloriously feral 4,0-litre twin-turbo V8 cleanly onto the macadam. Indeed, under hard acceleration, more than one member of the team felt an unnerving touch of fishtailing floatiness as the C63 set its traction-control light blinking … at 80 km/h. But that’s not the end of the powertrain quirks. While the Audi’s eight-speed torque-converter ‘box meshes well with its engine, the C63’s ‘box occasionally shows a tendency to abruptly shunt when coming to a stop on a trailing throttle.

An annoying lack of low-speed creep aside, the BMW’s dual-clutch unit is an absolute gem, snipping through the gears swiftly and assuredly. It’s also the most satisfying to manually operate, responding crisply to each tug of the paddle where there’s a touch of hesitancy in the others. The M4’s outputs sit neatly in the bracket that balances off-the-line control and punch, as evidenced by a 0-100 km/h time that’s only marginally eclipsed by that of the grippier Audi. Throttle response is also more measured in the M4, allowing you to put down the power more progressively than the sometimes hair-trigger sportiest setting in the RS5 and the C63’s all-and-nothing delivery.

If there is a mark against the M4’s motor, it’s a largely subjective one; its raspy exhaust note isn’t the most appealing of the trio, lacking the RS5’s distant howl and upshift thrumps, and certainly not in the same league as the indulgently guttural C63.

Off the leash

While the contest has thus far been a fairly evenly matched affair, it’s on the open road where one competitor comfortably noses ahead of the pack, and it’s not the C63 S. If ever a car adhered to the old adage that absolute power corrupts absolutely, the AMG is it. It’s not all bad news, though. The C63’s steering is quick and responsive, while the direct manner in which it noses into bends is pleasing. But, when dumping the throttle, the chassis is overwhelmed by the power on tap and such alertness largely counts for little.

To the adept driver, there’s plenty of appeal in the C63’s willingness to use a balanced throttle to steer its tail in a drift, but the margin between having fun and “hail Mary!” is all too abrupt, lending the C63 an unchecked boisterousness that, while initially entertaining, can become tiring. Factor in that creaky cabin and rock-hard ride, and the C63’s appeal begins to wane once away from back-road blasting.

And it’s not the RS5, either. The team was unanimous in its praise of this car’s well-damped ride and good NVH suppression, making it the most liveable of the trio on an everyday basis. But this mild-mannered demeanour largely clouds what character is required to make it a more balanced performance car. Often we confuse heavier weighting as an indicator of steering quality, but setting the sportiest configuration only serves to make the helm decidedly leaden. Many of us were pleased to see that the Drive Select system allows you to select a lighter steering setup alongside a sportier powertrain setup.

Aud RS5 Coupé vs. BMW M4 Competition Pack vs. Mercedes-AMG C63 S Coupé
If there’s one thing you can say about the RS5, its that the sheer levels of mechanical grip served up by its AWD system makes it feel supremely planted in all conditions. As is to be expected of a vehicle powering all four corners, the result is predictable but fun-curtailing understeer. There’s something of a disconnect between driver and car, perhaps the upshot of that massive grip and a chassis that’s geared more towards comfort than communicating its intentions.

It’s a criticism that simply cannot be laid at the M4’s feet. Its ride, although not quite as composed as that of the RS5, is still tolerable enough in everyday driving. However, when pushed, the M4 shines. The chassis’ impressive tuning means that you can feel exactly what the car is doing beneath you; when grip is giving way to slip and resisting lateral pull with greater composure than either of its rivals.

Then there’s the steering, which is more forgivingly weighted across its various settings than the RS5’s and echoes the chassis’ feelsome nature in a manner that communicates exactly what the car’s mid-corner attitude is. The more progressive power delivery furthers driver confidence, allowing you to gently push against the envelope of your skills without the fear of being unable to detect the point at which you’d otherwise pirouette off the black-top.

In short, where the C63 makes you feel like you’re hanging on for dear life, and the RS5’s detachedness suggests you are merely a cog in a fast machine, the M4’s poise and precision makes you feel very much part of the driving whole.

How much is that pit bull in the window?

It must be noted that squeezing the additional top-end performance from all of the cars here requires an additional outlay over that of the standard model. In the C63’s case, lifting the lid on the limiter to up the top speed to 290 km/h costs nearly R16 000. You’ll pay R97 000 to get 280 km/h out of the RS5, but this also introduces a sports differential, uprated steering and suspension, and matrix LED headlamps. The M4’s Competition Pack commands a R135 900 premium that, in addition to a 280 km/h top whack, bumps the power up by 14 kW over the standard M4, while also adding an active differential, sports exhaust and numerous cosmetic bits.



TEST SUMMARY

Reviewing aspirational performance cars always brings about something of an analytical tug of war between the objective head and subjective heart, where on-paper prowess doesn't necessarily determine the winner. That's very much the case in this particular comparative test, where numbers count both for and against the competitors.

 

In the C63's case, the numbers that stand out are those tarmac-rippling 375 kW and 700 N.m outputs. Although possessed of sharp responses and a chassis that lends itself to an aggressive approach, the C63's underpinnings are too tightly sprung and unforgiving much of the time. The more talented and steely nerved driver will no doubt enjoy the C63's visceral, tail-happy nature, but for most it makes the car one-dimensional yet twitchy. The C63 has something of the pub dog about it. One minute, it's wagging its tail and playfully eating crisps out of your hand; the next it's wrestling you to the ground, snarling menacingly with its jaws clamped around your wrist. We again can't help but ponder whether the C43, with its grippy 4Matic system and more forgiving ride, isn't the better buy...

 

Audi's engineers have placed their charge on a far tighter AWD leash and the result is a bizarre mixture of "formidable" and "falling short". The on-paper figures place the RS5 ahead of the pack in most respects: it blitzes its rivals in the standing-start sprint stakes; has the most solidly constructed cabin; and is more refined and easier to live with. Compared with its rivals, the RS5's prodigious grip and predictable handling make going fast almost comically easy. But that effortlessness is what ultimately hamstrings it.

 

There's the nagging feeling that this RS5 has an air of unrealised potential about it. While it's satisfying to have such ballistic performance just the flex of an ankle away, once up to speed and presented with tight, twisting roads, it's the drivers of the C63 and M4 who'll be having more fun. Perhaps it's down to the decision to retire the previous car's glorious, naturally aspirated V8 in favour of an all-new turbocharged V6 that, while mechanically accomplished, lacks the previous engine's charisma. Some of the CAR team felt that the RS5 could've handled more power and benefited from increased visual and aural drama. If this sentiment were to gain enough traction globally, would Audi even consider a "Plus" model?

 

Sitting squarely in the Goldilocks zone of "just right", the M4 proves to be the most rounded product in this shootout (and, curiously, a more planted, appealing performance car than the M4 CS we tested at Performance Shootout 2018). There's enough power to lend it a wicked turn of pace without the tyre-shredding mayhem of the C63 and, while not quite as everyday-friendly as the RS5, it has just enough leeway in its demeanour to make it reasonably liveable. But its trump card is its ability to communicate its every intention to the driver, making an average driver feel accomplished and a skilled driver heroic. The M4 gently encourages its pilot to explore their ability a little more each time, while being just about forgiving enough should they stray a little bit beyond their capability.

 

Admittedly, these are not quantifiable virtues, but the others here simply cannot match the M4's human/machine interface, and it's that tangible connection that sees it edge the RS5 in this instance.

 

*From the February 2018 issue of CAR magazine