Luxury Sport Convertibles Comparison

Our Sport Package-equipped Z4 was fitted with the optional 3.0-liter/225-horse straight-six engine mated to a slick new six-speed manual transmission. It delivers an impressive amount of power, with vibration evident only by its absence. While low-end torque is impressive, too, the Double VANOS variable valve timing comes to the fore at 3000 rpm, creating a surge of thrust that continues smoothly to the 6500-rpm redline. Underway, dual exhaust tips broadcast a turbine-like mechanical growl that's wired directly to the driver's right foot.

A rigid structure and quality underpinnings give the Z4 confidence-inspiring manners. Struts in the front and a multilink rear suspension, sourced from the current-generation 3 Series, give impressive feedback without harshness. Guardian-angel-like Dynamic Stability Control is standard and can save your butt, yet is pushbutton defeatable. The Z4 is sensitive to front/rear weight transfer, rewarding throttle/steering smoothness with high levels of cornering grip. Electric power steering gives a light feel at parking-lot speeds, but firms up noticeably on the highway. All of these engineering elements have coalesced, resulting in a sports car that can handle daily commutes and canyon carving with equal aplomb.

In the other corner is Porsche's Boxster S, the well-established German roadster. This year, horsepower has been nudged up from 250 to 258, with torque increased four lb-ft to 229. Like most opposed-cylinder Porsches built in the last 50 years, this engine comes alive under a heavy whip. The S' 3.2-liter six-cylinder generates max power at 6250 rpm. Our favorite part is when the VarioCam system segues to more aggressive valve timing with a wonderful, warbling combo of intake and exhaust sounds. And it's smooth; the need for an upshift is often indicated by the rev limiter.

Handling can best be described as kart-like, as translated to a street machine: a midship seating location combined with razor- quick directional transitions. Feedback is instantaneous, with only a hint of cowl shake on B-road rubble. MacPherson struts at each corner deliver a firm ride without being abusive. Unless the driver makes a living by racing Porsches, leaving the stability-management system engaged could prevent sheetmetal modifications. Driven intelligently, the Boxster S makes a fair driver look good and a good one even better.