The Mercedes, for its part, boasts variable ratio steering that quickens during aggressive driving. We feared this would feel unnatural, as many such setups are, but Mercedes has executed it nearly to perfection. The variable effect is transparent, and the steering itself is light, precise, and extremely communicative. We wish we could say the same of the Z4's steering. It's a variable effort setup that seems to have two settings: "heavy" and "heavier." We'd happily live with this extra forearm exercise if the reward was excellent feel and feedback but, sadly, it is not.
The BMW Z4 sDrive35is proves once and for all that a hardtop convertible can be aggressive, macho, and sporty. And yet, the Mercedes-Benz SLK350 is also aggressive, macho, and sporty without needing to prove it constantly. It looks muscular without a million creases in its sheetmetal; it handles well without the pretense of heavy steering or adaptive dampers. If you want a the most performance and attitude you can get for your dollar, then by all means, go for the Z4 and its iron-fist-in-a-velvet-glove powertrain. Just make sure you don't actually want a Porsche Boxster, first. Most hardtop convertible buyers, however, would do better to choose the SLK350, which provides as much real world driving pleasure but never hides or apologizes for being what it is: a very comfortable, stylish hardtop convertible.