Mercedes SLK 350 7G

Until the SLK 55 AMG joins the range early next year, the 350 is the fastest SLK you can buy. A real head-turner, with a driving experience that is light years ahead of its predecessor, this is a Mercedes that should be taken seriously. However, Porsche's Boxster is considerably cheaper, and will prove hard to resist for premium roadster buyers.

Sibling rivalry has reached melting point at Mercedes. Until now, the undisputed king of cool has been the flagship SL - but suddenly, this car is feeling threatened by the cheaper, but equally impressive SLK.

That might be bad news for the big cabriolet, but it's even worse for the SLK's conventional rivals, including the Porsche Boxster and TVR Tamora. Both boast impressive performance, but can the duo deliver the refinement and desirability the new Mercedes offers?

We've already been impressed by other models in the range, but the 3.5-litre machine promises to improve the roadster's reputation still further. Equipped with the firm's latest 272bhp V6 engine, this SLK feeds its power via a seven-speed automatic transmission. While there are no complaints about the performance, with 0-62mph in 5.5 seconds, we're still not convinced about the merits of this box over Mercedes' conventional five-speed automatic. With so many gears to choose from, it can feel a bit fidgety, and it isn't quite as smooth as we would have hoped.

However, this is just about the only criticism we can level at what is an extremely competent roadster. Once you have got used to the slightly heavy steering, you will enjoy one of the most convincing driving machines Mercedes produces.

So is the SLK 350 good value for money? Well, it might be some £2,511 more expensive than the nifty Porsche Boxster Tiptronic, but we think it's every bit as driveable, and equally aesthetically appealing. Meanwhile, buyers who find themselves behind the wheel of the new model alongside a larger SL 350 ought to feel smug about the £21,300 they have managed to save.