the springs on the clutch do a lot for saving the transmission. Why would one be harder then the other, well if there is a shock load presented by having stiffer springs, and stiffer enguagment with the flywheel the forces to the transmission are going to be greater and therefore harder on the transmission. A racing clutch is definatly going to be harder on the transmission than a stock one. Not to mention that RPM will have to be higher to properly enguage into first.

Please someone correct me if I am wrong, but thats how i see it