Check out MotorTrend’s BMW / Mercedes stack-up video, in which we find that even with the MBZ featuring all-wheel-drive- the two super sedans are evenly matched, generally!
One interesting tid-bit; they run both cars through the dynamometer to gauge how closely they match the manufacturer’s horsepower rating. The BMW under-performed slightly, while the Mercedes exhibited much higher horsepower and torque readings than what Mercedes-Benz advertises.
Lots of great footage of both cars in this great match-up video.