For those who appreciate and get some benefit from the rear seats, the BMW has some added value (as long as those passengers are not taller than five foot six and don't mind traveling with their backs in an exceptionally upright position). The luggage capacity is, however, just marginally bigger than that offered by the SL: 12.4 to 12 cubic feet, with the top up.
One of the main improvements the new SL has is in the engine, which now has a 5.5-liter displacement and generates 382 hp, and 391 lb-ft of torque available from 2800 rpm. Despite the 26-percent power increase, fuel consumption has decreased very slightly. But there is still a more progressive and prompt response than with the previous SL550. The new seven-speed transmission (with a Sport program which makes shifting 30 percent faster) allows greater exploitation of the car's performance while lowering carbon dioxide emissions (which nevertheless are higher than the BMW's).
An obvious element to the Benz's improvement in handling is its new direct steering. A variable system (simpler and cheaper than the active steering arrangement from BMW) performs in an equally satisfactory way. Even through the most compelling curves, there's never that odd `more hands than wheel' sensation. Even in the situations where the front wheels must turn through 90 degrees. The combined effect of the steering feel, body control system (both cars have their own versions) and the refined chassis tuning makes this is the sportiest SL ever. It gives nothing away to the BMW in this respect (which was not the case with the previous model).
A playful driving style may even be adopted in total safety by disconnecting the stability control and teasing it through sharper turns, where it responds by displaying a tail-happy character. If up to now the 6 Series Convertible was the sole bearer of the Most Efficient Luxury Convertible crown, it now has to split it with its Stuttgart arch-rival.
Under braking, no fading problems were felt on either car, although BMW's brake pedal provides a better response. On the other hand, the SL has a slight advantage, again thanks to the seven-speed transmission (which is also easier to handle since upshifts are executed with the right pad and downshifts with the left. In the BMW, you shift up by pushing and down by pulling either pad). Anyhow, when provoked to their maximum, both all-aluminum V8 engines move their masses with a truly impressive celerity. The automatic gearboxes glue occupants to the backs of their seats when the kickdown comes into play.
Both chassis make use of independent suspensions, benefit from a healthy weight distribution, rear-wheel drive and sophisticated stability control systems with ABS, traction control and corner stability functions. The availability of sport programs in both gearbox and throttle is truly welcomed when in the mood for more enthusiastic driving.
Last but not least, the SL must be praised for its superior nimbleness, which derives from its smaller dimensions. It's also more suitable for urban driving (especially when having to park or perform 180-degree turns in the minimum possible space).
2009 Mercedes-Benz SL550
Layout
Longitudinal front-engine, rear-wheel drive
Engine
5.5-liter V8, dohc, 32-valve
Transmission
Seven-speed automatic
Performance
Peak Power: 382 hp @ 6000 rpm
Peak Torque: 391 lb-ft @ 2800 rpm
0-60 mph: 5.3 sec. (est.)
Top Speed: 155 mph (electronically limited)
Dimensions
Length/Width/Height (in.): 179.6/71.6/51.1
Wheelbase 100.8 in.
Curb Weight 4,202 lb
Price $95,300 (est.)
2008 BMW 650i Convertible
Layout
Longitudinal front-engine, rear-wheel drive
Engine
4.8-liter V8, dohc, 32-valve
Transmission
Six-speed automatic
Performance
Peak Power: 360 hp @ 6300 rpm
Peak Torque: 360 lb-ft @ 3400
0-60 mph: 5.6 seconds (est.)
Top Speed: 155 mph (electronically limited)
Dimensions
Length/Width/Height (in.): 190.2/73.0/54.1
Wheelbase : 109.4 in.
Curb Weight: 4,277 lb
Price: $82,700