They may be alternatives to their fire-breathing siblings, but these business-suited sports coupés are spoiling for a fight. Yes, it's the Audi S5 Coupé 3,0T FSI Quattro Tiptronic versus the Mercedes-AMG C43 Coupé 4Matic 9G-tronic...

Alternative is a funny word. Put it in front of “accommodation”, “medicine” or, indeed, “music”, and it likely elicits an unenthusiastic response from those less enamoured with hotels in a “colourful” part of town, the medical application of leeches, or the acoustic nuances of the sitar. Thankfully, with the myriad variants and vehicle niches opening up daily, car buyers are assured that having an apex model lie just beyond your reach doesn’t necessarily mean that the alternative leaves you feeling shortchanged.

In the performance-car sphere, however, 2% often isn’t a substitute for full fat. Those whose budget falls just short of Mercedes-AMG’s V8-equipped sledgehammers, or the Bauhaus bullets that are RS-badged Audis, will probably feel aggrieved at the idea of settling for cars that bridge the gap between each firm’s workaday models and the aforementioned fire-breathers. But, in the case of the Mercedes-AMG C43 and Audi S5, these alternatives may no longer be a concession.

There’s the mouth-watering making of a closely contested fight here. While the heavyweights often clumsily swing haymakers and the lightweights partake in a comical-looking dance of spindly legs and pillow-sized gloves on windmilling arms, these middleweight bouts are the ones to savour. They pit similarly matched boxers in a fast-paced fight where skill often supplants raw power as the winning factor.

The meeting of alternatives may technically be an undercard event to the harder hitters, but this middleweight bout is likely the most heated exchange you’ll see between two German performance cars in some time.

Tale of the tape

In every good middleweight bout, the opponents are closely matched and this certainly holds true of the contenders here. Both are underpinned by all-wheel-drive systems fed by turbocharged 3,0-litre V6 engines. Although the 250 kW and 500 N.m outputs of the S5’s all-new engine are 15 kW and 60 N.m up on the previous car’s, the AMG-fettled version of Mercedes’ biturbo V6 is the marginally harder hitter to the tune of 10 kW and 20 N.m.

Both feature rear-drive-biased all-wheel-drive systems (40:60 in the S5 and 39:61 in the C43), with the Audi’s underpinnings incorporating longitudinal torque-apportioning via a mechanical centre differential that can send up to 85% to the front and 70% to the tail, depending on driving attitudes. It’s augmented by a lateral torque-control system that uses ABS to brake the inner wheels under hard cornering in a bid to tuck the nose into a bend and mitigate the understeer so typical of all-wheel drivetrains.

The C43’s setup is more straightforward, locking the apportioned torque and relying on a battery of sensors to detect conditions underfoot and cut power, or apply ABS and stability systems, to best aid traction. In fact, the greatest difference between the two is apparent only in their approaches to the ring.

Ringside entrances

Entering to fanfare, dry ice and a lightshow is the C43. Although it’s viewed as a stopgap between the four-cylinders and AMG V8s, its promoters see it as a fully integrated member of the AMG family, standing alongside more powerful hardware in its stable. Consequently, we have a middleweight that looks like it occupies a higher class. Along with bulging wheelarches, moulded skirts, vent-studded aprons and the generous application of chromed “biturbo” lettering on the flanks and tail, it looks every bit a member of Affalterbach’s stable and will therefore appeal to those wanting the world to know that their car means business.

But such arrogance isn’t for everyone and the S5 is very much the purposeful shadow boxer to AMG’s showman. With just the subtlest of go-faster accoutrements – 19-inch rims, the merest hint of a boot spoiler, modest skirting and subtle S badges – applied to a smooth-skinned and conservatively upmarket frame, the S5 has a distinct Q-car charm that will appeal to those who like to feint before landing a knockout blow.

Inside, it’s a similar story; the S5’s cabin is a study in understated sportiness, here featuring deep-red leather seats and seams of aluminium running through an interior that’s materially superior and marginally more spacious than the C43’s characterful but more close-fitting cockpit. In both cases, you find yourself in a purposefully low-slung driving position, held in by seats that are supportive and bolstered a touch more sympathetically than those of their more powerful peers.

With the aesthetics and posturing dispensed with, it’s time for gumshields in grilles and seconds out as the open road beckons.

The first salvo

On paper, the S5 has slightly faster hands than its rival. Its maximum torque chimes in at a low 1 370 r/min and spreads itself over a broad plateau that tails off at the 4 500 r/min mark; the C43 counters with a 2 000-4 200 r/min spread. But, in practice, the difference is largely negligible, with a glance at the straight-line performance figures revealing a 100th of a second here and there in the more powerful C43’s favour. Although closely matched in the numbers, these are two cracking engines with distinct characters.

Coupled with an eight-speed torque-converter ‘box, the S5’s unit feels more languid and marginally slower to spool up than the C43’s. What’s more, with a touch extra dead travel in its accelerator pedal than the C43’s hair-trigger of a throttle – something that can be a little challenging when the car is in its full-attack sport+ setting – there’s a bit of a “one-Mississippi” moment before it hunkers down and surges forward with a satisfying, if somewhat subdued, howl from the tailpipes.

To its credit, that broad torque spread means that the S5 feels longer-legged and more of a fast grand tourer than the C43. By contrast, the AMG, with the flaps open in the adjustable sports exhaust system and the riot of hollow-chested bellows and snaps it brings, gives the impression of being the more alert of the pair, throwing plenty of leather when driven with gusto. The sense of immediacy in the engine’s free-revving nature is furthered by the transmission’s willingness to jab through the gears.

With a nine-speeder, there’s always the concern that the ‘box will hurry to the higher ratios for efficiency’s sake. However, regardless of how it was handled, the C43 never seemed to miss a step, smoothly and swiftly swapping cogs, while the S5’s similarly silkily shifting unit clinched tenaciously onto gears when leaning on the throttle. The previous S5’s snappy, smile-inducing downshift throttle blips are more subdued now, but otherwise the new car’s ‘box serves up a smooth, measured performance that lends itself well to briskly covering long-distances.

Bob and weave

Audi’s above-mentioned claim that the S5’s all-wheel-drive system all but banishes understeer is not a hollow one. Its blend of directional accuracy and limpet grip when pushed on a twisting road thoroughly impresses. But it was the C43 from which all of the CAR testers emerged grinning from ear to ear. While the Audi feels planted and oh-so-grippy, it’s also a bit anodyne in some respects. Although you can confidently barrel into a bend and stamp on the brakes before bulleting out the other side without any loss of composure, the variable-ratio steering rack, although pleasingly weighty,  just doesn’t have the immediacy and responsiveness of the C43’s much lighter, more accurate helm. And, while you can’t always detect how much that Quattro system is churning away beneath you, the C43’s fixed split is managed in such a way that the intervention of the electronic safety net is unobtrusive, with the approaching limits to grip announced by just a smidge of tail-end lightness.

The S5’s cornering attitude feels flatter than the C43’s, but the latter’s degree of body roll is progressive and not at all intimidating. The way it carries itself through the curves, mixing plentiful grip with responsive controls, is almost akin to piloting a rear-wheel-drive car, making the C43 the livelier of the two. A couple of testers even went as far as suggesting that this middleweight has the goods to best some of its more powerful stablemates by allowing an average driver to confidently cover challenging roads quicker than in the C63.

While the S5 can’t quite match the C43 in a brawl, it acquits itself more ably than its opponent when more measured driving is the order of the day. In terms of refinement and relaxed driving manners, the S5’s less frenetic nature gives it an edge over the C43 as a sublime long-road cruiser. That said, the S5’s adaptive suspension, although impressively composed for the most part, gets flummoxed by sudden changes in road surface and becomes crashy at times. The C43’s ride is notably firmer, but it’s more consistent in its manner. Both cars ably pull their punches, returning sub-three-second 100-0 km/h braking times, although the S5’s pedal is a hair less responsive than its rival’s.

Fight purse

Again, there’s not much in it here. The marginally cheaper Audi is slightly better equipped in its standard form than the C43, but the AMG car counters with a maintenance plan that’s a year longer. As is often the case with German cars, options will see the price heading northwards at a rate of knots. Our S5 test unit bore more than R232 000 worth of extras, including sat-nav, an uprated audio system, keyless drive and the very slick LCD Virtual Cockpit instrument binnacle.

Speccing the C43 can also break the bank, with such extras as the sports exhaust system (an R18 900 option that really should be standard) quickly bumping up the price. Both cars have a similarly hearty appetite for unleaded, quaffing around 10,0 L/100 km on our mixed-route fuel run.



TEST SUMMARY

Two points are all that separate these two swift and capable cars, so the buyer's decision could come down to brand affinity. Their positioning is also a factor. Although broadly viewed as in-betweeners, the gap separating the C43 and C63 isn't as apparent as you'd imagine, and given that the next RS5 will likely sport a twin-turbo V6, it's understandable that Audi doesn't want the S model to tread on its toes.

The more mature S5 is beautifully crafted, just about practical enough to ferry passengers and still has a wicked turn of pace; it's a car you could happily live with on a daily basis. But the C43, although shoutier, isn't that much less liveable and manages to dynamically engage and satisfy in a manner that the more restrained S5 cannot.

And it's that extra dimension to the C43's persona that sees it outscoring a very impressive opponent by a small margin.

*From the June 2017 issue of CAR magazine

Original article from Car