My guess would be the runflats and the fact that you have much more instantly available power on the 335. I've flogged both of these cars on uneven pavement...breaking the read end loose on both. The 335 always felt more controlled. Remember that on the 3...if you're in second gear and floor it you have all 300 ft-lbs of torque immediately. The G in the same conditions needs to build up to its 270 ft-lbs of torque much more gradually with its naturally aspirated engine.
Lightly tuned Montego Blue 09 335 with a clutch