Max Machler, the European AMX team manager, TQed and won the Spec GT class, at IIC. Luke Pittman with a T4, TQed and ran 2nd in Stock. Both drivers SHOULD have been running in Mod. Even Scotty made comments to that affect.
I did see independent drivers that did very well with both chassis. One was not BETTER than the other. If you like to tinker, AMX is for you. If you want a tank, go Xray.