I dont think a 240 has more potential to be better then a hatch, and in the end it all depends on the driver. You can make a hatch a lot faster on an autocross course then a 240 price wise and probably just setup.

I say just get out there and have fun. It takes a LOT of practice to win. It is a lot of fun, no matter how fast you are. Start stock and start buidling up little things at a time.