" Here are two beautiful luxury convertibles from Jaguar and Mercedes-Benz both with boosted V8's and both sending power to the rear wheels. The R231 SL63 AMG is leaner and meaner
than the previous generation R230 model. It has a twin turbo 5.5 liter M157 V8 under the hood putting out 530 horsepower and 600 pound-feet of torque. The XKR-S has a 5.0 liter V8 under the hood but it is supercharged giving an output of 550 horsepower and 501 pound-feet of torque.
So more power on paper but less torque for the XKR-S. You might think power to weight would be in its favor with its convertible soft top versus the hard top on the SL but at 4,079 pounds it barely undercuts the 4106 pound SL63 AMG. Torque to weight is certainly in the AMG's favor and if these cars hit a dyno power to weight likely would be in the SL's favor also.
The SL is the first to hit the track and does a 1:23.9 laptime. It is more of a GT than a sports car but it shows minimal body roll. The XKR-S is said to feel lighter with its steering but that it has more body roll. It also struggles to put its power down essentially constantly wanting to be sideways. That certainly is a fun personality compared to the SL63's business like demeanor but it does not result in a quicker lap. The Jaguar does a much slower 1:25.7.
The Jaguar certainly appears to have the more entertaining personality of the two but it also looks to be a bit of a handful that struggles on the track. Is that more fun? Well, that depends on your personality. "