Is the only difference between these two ESC the motor limit, I am looking at getting one of the two, I was looking the specs over and I think that the motor limit is the only difference between the two is this correct??

Also lower ON resistance. It's more efficient and will likely run cooler because of that.

So which one would run cooler the FX or the FX pro??

your best bet is to ask Randy Pike from Tekin. You can PM him here on rctech or e-mail.
His e-mail addy is [email protected]

THX