The snow falling from the leaden sky over Pffanhausen made me nervous. As did the fact that Natalie Campagna, Keeper of the Keys for RUF Automobile De, couldn't look me in the eye. And no wonder: Alois Ruf himself had just called to forbid the English journalist from driving the R-Turbo. On the face of it, it was an entirely sensible decision. Five hundred and twenty horsepower and drifting snow are not the ideal combination for a test drive- especially when the car in question belongs to a customer.

Plan B involved a ride in the passenger seat with a RUF technician at the helm, followed by a 'small spin behind the wheels.' As I helped push the immaculate R-Turbo out of the showroom, I hoped something had been lost in the translation. I took comfort in the fact that RUF's official press car- a yellow, rear-wheel-drive machine-was busy making sushi out of lesser cars in Japan. This silver car had four-wheel-drive and stability control. Oh, that's all right then… isn't it?

Blasting down an unrestricted section of autobahn at 125 miles per hour, the new Mercedes SL did something extraordinary: it kicked down. There I was, as nervous as a human cannonball aimed at a brick wall, and the SL just reaches down, grabs some more power, and slings me all the way to 155. All my doubts about Mercedes' range topper vanished. It's totally safe, faultlessly efficient and plenty damn fast. It is, in fact, the perfect car.

Oh, OK, the turn indicators sound cheap and nasty. The vanity mirrors are too small, and lack an indent for easy opening. The driver's visor is too tightly sprung; try to find a shallow angle and it just might snap your fingers off. And, um, that's it. It's perfect.

Speed matters. So does size. A Lamborghini Murcielago can crest 200mph on an autobahn, but it’s slower than a pair of roller skates down a busy city street. Enter Mercedes’ chic new SMART car. It’s tiny– small enough to dart through any gap wider than an NFL lineman. It’s quick– well, “nippy”. It uses less fuel than a John Deere lawn mower. In fact, the SMART should be an urban driver’s dream come true. It isn’t.