Speed Week: Porsche Cayman vs Merc A45 AMG

Try saying this without sounding ridiculous: "A Mercedes-Benz A-Class and a Porsche have similar performance and aren't so different in price." But, of course, we're talking about a special kind of A-Class. By levering its power beyond 350bhp and its price toward £40,000, Mercedes-AMG has kicked the A45 clear out of the hot-hatch park. Very well, then - let's line it up against the closest rival we have here, the Cayman. They both come with cast-iron brand reputations and a sense they've been lovingly assembled by dedicated craftspeople out of the very best components. They were both conceived in the same city, Stuttgart. Beyond that, they're polar opposites. Longitudinal mid-engined versus transverse front-engined. Flat-six versus turbo four. Rear-drive versus AWD. Two-seat coupe body versus a five-seat, five-door hatch.

And yes, they're as different as that to drive.

Open the door to the Mercedes, and you're in a normal hatchback driving position. Mind you, AMG has given it some love. The big seats are terrific, plush on the road and grippy on the track. You fondle a suede-rimmed wheel. There's an AMG gear selector below the centre console, rather than Mercedes-Benz's column wand. Little aluminium gearshift paddles give more reason for optimism.

But the Porsche is a sports car. You drop into its cockpit, and it's as low as a snake and just as ready to twist and turn. This one's optioned to be near-optimal for the task in hand: one-piece bucket seats, big wheels, adaptive chassis, sports exhaust. Simple steering wheel with no buttons, because its job is to steer. Three pedals and a manual gearbox amplify the message that driver and car must work together.

The AMG's powertrain gets the headlines. How can they squeeze 355 horses out of two litres? By strengthening it all, then bolting on a humongous blower. As always with this kind of installation, you get lag. Though there's huge mid-range torque if you wait for it, the delay isn't properly gone until 4,000rpm. Which is a pity, because the engine revs only to 6,250rpm, so the best bit of the powerband is squeezed from below and above. Get the thing on the boil, though, and there's mighty thrust. But don't expect any help from the gearbox in keeping it in that sweet spot. The upshift paddle imposes a dopey delay. Neglect to allow for that, and you'll be stuttering on the limiter. And asking for downshifts, even when there's plenty of rpm headroom, often meets with sullen refusal. The engine sounds OK, with a bit of encouraging popping from the exhaust, but basically it's a one-dimensional drone.

The Porsche, too, keeps you busy with its manual gearbox, but the whole process is involving and joyful enough to be recreation in itself. The wonderful precision and immediate response from the throttle pedal, the exact travel of the clutch, the slack-free oiled movements of the gearlever. Sure, a PDK might be faster, but we're here to drive, aren't we? Anyway, the six-speed 'box's ratios seem better spaced and suited to this track than the AMG's seven. The Cayman's engine sonics are gorgeous, too - the textures of exhaust and intake and mechanical beats getting a remix every time you so much as twitch your right foot. And as you swing out of the middle revs, the power swells with relentless urgency to the 7,500rpm red line. That wider rev band and the fact you can time your gearshifts with more precision than in the Benz means I never feel a power deficit in the Cayman.

On the road, the A45 is grippy and not too hard-riding, but even out there, you can provoke understeer by barrelling too fast into a bend. On the track, that initial understeer dials itself up to a whole other level. If you don't get your braking done right, it's like the front end has turned to marzipan. Oh, and on the steep downhill braking zone, it keeps you busy by weaving about a bit too, and there are places where a bit more body control wouldn't go amiss. So, plan on using the four-wheel drive. Go in gently, get it turning nicely, then just nail it and it'll scrabble gamely for the exit, its stance resolving into nicely neutral. And the steering's got a nice weight and precision to it. But that's about it. Even ESP-off, there's not much in the way of options, at least not in Charade's mostly tight turns. Only on the fast right-hander near the end is there much chance to play a little with the slip angles.

The Cayman feels made for this track. But, then, I don't recall driving a new-gen Boxster or Cayman down any road or track anywhere and not feeling it was absolutely in its element. It's all about precision and control. The suspension breathes its way over bad bumps but keeps itself damped with ice-cool self-restraint. Pile into a bend, and the car follows your thoughts. There seems no interposition of steering suspension calibration here: I found myself having to consciously analyse it, because it simply feels so right it's not immediately clear why. It's down to the ideal gearing and response of the steering, the progression of the roll angles and turn-in, the harmony between the front and rear ends. Through the apex and out, there's traction enough that you feel it'd happily take more power if only Porsche would allow the Cayman to reach its potential instead of endlessly protecting the sanctity of the 911. The Cayman's balance is as sweet as you like, and amenable to being trimmed. A little lift will tuck the nose in, a bigger one will edge the tail out so you can hold it with power, and always the steering and the progression of all its responses will back you up.

It's only after I deliberately applied my mind to the matter that it dawned on me there's actually not a whole lot of true steering feel. On a dry track, this doesn't matter a bit because the messages from all of the car's other organs are so unambiguous, but on a damp road it does rob you of confidence and the final ounce of intimacy that we remember from the original Caymans.

Lower weight mounted lower, more agility through a lower polar moment and a slightly better power-to-weight ratio: the numbers say The Stig is going to be faster in the Cayman S than the A45 AMG. I stand back and watch that very result unfold. But even if the A45 had gone faster, the fact is that it can't hold a candle to the Porsche in the things that made us fall in love with driving: the sense that you're not just riding in a machine or fighting against it, but that you're so intimately connected as to have become part of one whole exquisitely functioning mechanism.

Photography: Rowan Horncastle