Mercedes-AMG C43, part of the new four-wheel drive, turbo V6 powered 'junior' AMG line-up and a tad more expensive than the £45,400 Audi at £46,255. Low speed steering chunter aside we liked the Mercedes when we drove it last year but, at this price and performance point, the S4 Avant is very much the car to beat. And if you don't need an estate you can have it as a saloon for £1,400 less.
As you're probably aware by now the S4, like the S5, uses a new turbocharged 3.0-litre V6 with 354hp and 369lb ft. It's 21hp and 44lb ft up on the previous supercharged V6 but weighs 14kg less too - welcome given its traditionally Audi positioning ahead of the front axle. The S Tronic dual-clutch has been replaced with an eight-speed auto and the whole car is 75kg lighter than its predecessor.
It's a handsome thing too. Yes, A4s are a regular sight on British roads, especially ones decked out in S Line trim. So equipped there's little to set an S4 apart from a regular car - you can even put these optional (and rather tasty) 19-inch wheels on a 2.0 TDI if you so wish - but the chrome mirrors and quad exhausts are subtle reminders to your Audi brethren of where you sit in the fast lane pecking order. If the shape is conservative and familiar to a fault it's also subtly attractive, understated sculpting to the flanks giving it quiet poise and Ingolstadt cool against the fussier styling of the 3 Series and C43.
Same inside too. The unique to the S4 S Super Sport seats feel as good as they look and - whaddya know - the cabin combines crisp design with excellent ergonomics and lots of gadgets and gizmos. Where Mercedes is currently in one of its chintzy phases the S4 continues to refine the modernist minimalism so beloved by Audi fans.
All S4s run the 23mm lower Sport suspension over regular A4s, our long-termer also getting the £900 Adaptive S Sport Suspension (a 'civilian' version of the same is available for non-S4 models) you can set up via the modes in the Audi Drive Select. Revelations are few and far between in the conservative world of Audi but here's one - the S4 rides really rather nicely. As we know, there are good fast Audis and there are bad ones; the combination of float, flow and body control in the S4 is the first sign it might be one of the good'ns. Nor does it lose the plot in the sportier settings either, only harder edged bumps thumping through and upsetting the calm.
Those familiar with the previous model will know the importance of ticking the box for the optional and fully active Sport Differential too; thankfully ours has it! While the standard car will do the usual brake-nibbling stuff to help the car into the corners the optional diff adds proper torque vectoring to the rear axle and a real sense of this influencing the car's attitude on or off the power. It's no Focus RS but the man from GKN we spoke to and helped develop the Ford's Twinster system rates the Audi set-up and, indeed, runs an S4 as his daily. As such the more assertively you drive the S4 the more it gives back, subtly rotating into the turns on the power and helping offset that traditional nose-heavy balance.
Huracan LP580-2 we drove recently is anything to go by) but the standard set-up is undergeared and over-assisted, giving you nothing to lean against just when you want to make the most of that diff. Could be worse - could be the £950 Dynamic Steering option...
The eight-speed auto doesn't seem quite as crisp as the previous S Tronic either or, indeed, as responsive as it is in other applications, most notably BMW's. It's slick in auto mode but frustratingly ponderous in manual, even in its Dynamic mode. Worse still it can spontaneously downshift several ratios when you only asked for one, going from fourth to first on a rolling approach to a clear roundabout on one occasion. It's clearly another Audi 'thing', depressingly familiar from A1 through to R8.
One step forward...
These niggles are amplified by the fact the rest of the package is so sweetly judged. Like the C43 the S4 is a 'making progress' kind of car, be that on motorway or back road. But for an Audi it feels unusually well balanced, those kilos they stripped out of the old car clearly removed from helpful areas.
So, good fast Audi or bad fast Audi? In the way of things the S models typically offer an 'all you'd really need' sensible pants alternative to the RS models with just enough extra sparkle to put some distance between you and the TDI driving masses. So it is with the new S4 and its strong response to the twin-pronged attack on its home turf from the 340i and C43. There's little to alienate the fans, but that it comes a dropped ball or two from fully converting the doubters is a frustration.
AUDI S4 AVANT
Engine: 2,995cc, V6 TFSI
Transmission: 8-speed tiptronic, Quattro all-wheel drive
Power (hp): 354@5,400-6,400rpm
Torque (lb ft): 368@1,370-4,500rpm
0-62mph: 4.9 secs
Top speed: 155mph
Weight: 1,750kg (EU with 75kg driver)
MPG: 37.7 (NEDC combined)
Price: £44,415 (As tested £49,770 comprising Misano Red paint for £645, Quattro sport with Sport Differential for £1,200, 19-inch diamond cut wheels for £550, Light and Vision pack for £750, Adaptive S Sport suspension with damping control for £900, Audi phonebox with wireless charging for £325 and on the road costs of £985)
[Photos: Chris Teagles]