BMW M6 Convertible vs Boxster S

Convertibles haven't thus far been regular TopGear performance-car fodder - traditionally, they've been too soft, too compromised and generally designed for posing not powering. But, in the past few years, the game has changed. These days, convertibles give their hard-top counterparts a run for their dynamic money. And they do it with extra high-def sensory input.

Words: Piers Ward
Pics: Joe Windsor-Williams 

This feature first appeared in the August 2012 issue of Top Gear magazine

The BMW M6 Convertible and Porsche Boxster S are in the vanguard of that preconception-busting, modern attitude. Between them, they produce 863bhp and 766lb ft of torque. Both accelerate from 0 to 62mph in less than five seconds (4.3 for the M6, 4.8 for the Boxster), and both will manage top speeds high enough for a non-surgical facelift (155mph: BMW, 172mph: Porsche).

Given these figures, it's hardly surprising that neither was lacking pace out on the track; even the serious supercars failed to pull away completely down the straights. And both put on speed with minimal fuss - planted foot, a couple of tugs on the paddles and hello to licence-losing rapidity. The slick, dual-clutch gearboxes help. You can arrive at a corner, bang down the 'box and get on the power early to sling up the straighter bits. Concentrate on mashing the throttle as soon as possible because of the instant and punchy power delivery.

In the case of the BMW, a little too instant if you've pressed the appropriate buttons. First lap in, exit of Chicago, and I got on the power gently. But obviously not gently enough: the M6 swung like a proper street fighter, tail desperately trying to arc west towards Guildford town centre. And it continued to fight its way up the straight towards Hammerhead, squirming and pushing. Hilarious powerslides are not a problem in the M6.

And that's just in Sport Plus mode, rather than everything off, which is a bit scary when you think about it. But you can rein the M6 in if you desire. Like the M5, you can alter the steering, dampers, throttle response, head-up display and gearchange. Once you're happy with a set-up, you can save it on one of the two M buttons on the steering wheel.

In other words, you can have a town mode and a maximum-attack setting for whatever sort of driving takes your fancy, and it's easy to flick between the two. But - fun and impressive as they are - none of this makes it a sports car. There are laws of physics involved, and a front-engined car weighing over two tonnes will always struggle to be crisp and accurate on a track.

The Boxster, in contrast, is much more surgical, especially at a place like Dunsfold. Mid-engined, lighter, plenty of grip and power - less boisterous than the M6, but ultimately more rewarding.

The Porsche is more precise and feels like there's a more direct connection, so it's easier to be smooth and eke out a better lap time. It keeps dialling up more and more speed without biting back, helped at every corner by the stunning brakes. It feels sharper, more precise, a real sports car. And it makes me want to drive it on the road, hard-edged flat-six yowl bouncing off the scenery.

But if we had to choose one to listen to all day, it would be the M6 - it's gruff and deep-chested and batters your senses from lower down the rev range. In either of them, you're not insulated from a single burble. From a purely selfish point of view, this is where convertibles score plus points - they sound so much better to the person actually driving them. Roof down, engine revved to the limit, and let your ears suck in the delicious noises.

But these two aren't just about the brawn and the bellow in the latest generation. The build quality in both is incredible, and refinement and ride are impressive, too. Both have a compliance that you'd never expect from a German performance car, but, ironically, this is also where they come unstuck. It's TopGear's Speed Week, and we need our favourites to make us smile. Refinement is all well and good, but not at the cost of feel.

And the BMW has too much of the former and not enough of the latter. The trouble is that by aiming for a more civilised experience, some of the raw appeal of old has been lost. It's as if a smattering of fluff has been added in. The M6 is trying to cover too many bases - GT, town, back road - without ever figuring out which one it's best at.

The Boxster has definitely lost some of the edge that the old one had, so it no longer has quite as much close-quarters feedback, but it's still a wonderfully balanced car. And it would be a great thing to own out in the real world because it does so many things so well. But this isn't the real world. And when we've got 15 minutes left to play at Dunsfold, both convertibles get left on the bench. Seems like TG can't help but be ruthless with the roofless...b