BMW USA is promoting the X5M through a video shot at the Laguna Seca race track. It is here where the German SAV accelerates side by side with the E92 M3, with each model trying to get out of the famous ‘Corkscrew’ corner first.
Who proved to be the quickest? well according to this promo, the BMW X5M due to its 555 HP managed by the xDrive all-wheel-drive system and the Torque Vectoring Rear Differential. 
Is that really enough for a vehicle that weights 5368 lbs to become faster on track than the 420 HP BMW M3? well if it involves a little bit of cheating then yes.
BMW M3 vs X5M Promo Video:

Source: BMW via YouTube