“The Cadillac makes more power and torque than the BMW, but it's hard not to miss the M3's smoothness. Also its near-absence of turbo lag, smoothness, and -- did I say smoothness?
Regardless, the machine wrapped around that V6 is fantastic. Onto the bones of the ATS coupe and sedan go 50 percent more spring rate, wider tires and front track (the coupe out-fats the sedan in the rear by 23 mm), and uprated bushings and ball joints. Additional underhood bracing and an aluminum lower body brace help raise torsional rigidity a claimed 25 percent. The differential is the telepathic, computer-controlled active unit also seen on the Corvette, and GM's Magnetic Ride Control dampers are standard. There are very large Brembo brakes.” -- Road &Track