How much of the R8’s sensational dynamics have been preserved in the translation from coupé to Spyder? That’s what Autocar’s Jamie Corstorphine was left to decide in this week’s Autocar magazine. That and whether it can out punch the recently revised Porsche 911 Turbo Cabriolet.

Driving the two back to back over the same stretch of road, the facts rapidly emerge. First, that although both cars are noticeably less rigid than their coupé equivalents, in neither is the degradation excessive. But over the toughest it is the Audi (£111,995) that flexes least.

The more interesting discovery is just quite how differently the Porsche (£109,048) and Audi go about tackling a tempting B-road, and what sort of kicks they serve up.

The R8 is more your classic supercar experience. Although it is one of the easiest to live with, it is still low and wide and, due to the driver’s proximity to the engine, rich with mechanical interaction.

Although the Spyder is softer than the coupé, it still turns with very little body roll, even with its magnetically adjustable dampers set in their more relaxed mode, and not once is it fazed by the evil crests, bumps and cambers that makes these roads such a test for a car.

The Porsche is a very different animal. And that’s down to torque – 479lb ft of it, all the way from 1900rpm to 5000rpm. The Audi, by comparison, needs 6500rpm to deliver just 391lb ft.

Porsche’s new 3.8 engine responds with almost no lag. This means that not only does this Turbo have more firepower than the last, but it’s also possible to meter it out more precisely. Net result? Much greater corner exit pace.

Once you become accustomed to just how accurate the 911’s throttle is, and how rarely you really need to call upon the Full Monty, oddly the Turbo feels less manic than the R8. This is partly because the revs are lower, but also because the engine feels further removed, like some magical nuclear reactor.

If that sounds uninvolving and unrewarding, it isn’t; it just needs a different mindset from the Audi, the sort that gains satisfaction from using a machine designed precisely for a purpose.

Which is quicker? Certainly the Porsche is easier to drive quickly on unfamiliar, narrow and unsighted roads, mostly because its torque advantage gains it so much time coming out of corners. No doubt if you drove the R8 with sufficient commitment it could match the Turbo, and on a smooth track it could well be quicker.

Which is the more rewarding to drive? Here in Wales, personally I prefer the Porsche, not because it has the better balance or the better engine, but because I find its controls instill more confidence. That’s a shame for the R8, because at its core it is the superior machine.

But the Porsche does not win this test, because while it might have a minor advantage in ground-covering ability, the Audi has it licked in the areas that matter most for open-top supercars. It is, night and day, the more desirable car – not my opinion, but that of everyone we asked on our travels. It also has the better hood – not the simplest or quickest, but the more theatrical and beautifully finished. Technically the open R8 stays truer to the coupé than the 911.

But the clincher is that the R8’s thrills are more accessible and more relevant, especially where these cars will probably be used most. The Turbo Cab impresses with crushing competence, but what it lacks is the one thing the R8 Spyder has in abundance: drama. And drama sells.

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