If your comparing the various ZTR's that use that engine there is little to no difference. I have run them both and can't tell. What ZTR's are you looking at?
Today I drove a JD front mount zero turn with the Kohler and it started right up no choke needed. It also seems to be good. Probably since it is more heavy duty than the never Kohler I has in a JD garden tractor 3 years back.