Used test – sublime soft-tops: BMW 6 Series vs Mercedes-Benz SL vs Porsche 911

Hefty depreciation means big convertibles often make great used buys. But should you choose the luxury of a Mercedes, the prowess of a Porsche, or the all-round talents of a BMW?...

Published18 June 2016

Our Verdict

This is a difficult test to judge, simply because the Porsche’s cost – both to buy and to run – skews things so considerably. Indeed, we did wonder whether we should even include it in this test, so vast is the difference. But on practicality and usability, it more than holds its head up against the other two cars, and so exceptional are its performance and handling that it is worthy of consideration – even with its vastly inflated price.

That might mean you have to look at an older Porsche 911 for your money than you will a BMW 6 Series Convertible or Mercedes SL. Or, you’re in the lucky position in which money is no object, then you might be prepared to splash out on the Porsche where you wouldn’t on the other two. Were that the case, you wouldn’t be disappointed. It is an exceptional car, a cut above the Mercedes and the BMW in the way it drives and the way it goes, and a genuine sports car rather than simply a sporty drop-top.

For all that, though, we simply can’t judge it as a more savvy used buy than the other two cars here. It doesn’t better them by the order of magnitude that its price and running costs demand, and while we wouldn’t blame you if you wanted to spend the extra to get the most enthralling car here, neither could we recommend that you did so if all you wanted was a comfy, luxurious two-seater.

By contrast, the 6 Series Convertible is the value proposition here. Next to the 911, its running costs are almost city car-like, with impressively high fuel economy, low tax, and cheap servicing costs. It’s also the cheapest to buy. But cars like this need to be comfortable, and with a ride that never fully calms down and vibrations aplenty, that’s an area in which the BMW struggles to deliver. We can’t argue with the good financial sense the BMW offers, or indeed the fact it’s a truly classy cabrio. But it isn’t the best used buy here.

That honour must fall to the SL. Its metal roof makes it quiet and cosseting with the roof up, and with it down, the lack of buffeting is incredibly refreshing. Superb seats make it comfortable, too, and while it can’t hold a candle to the Porsche in terms of excitement, it’s still entertaining enough for most drivers. Indeed, only a slushy gearbox spoils things slightly, but given the nature of the car, even this flaw is one we can overlook.

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