how much of a diffrence is it in power and cooling.

not relating to my xr6 but my r33 has a clutch fan, was going to change it but was told not to on other forums because thermo fans dont cool the car down nearly as much.

i know fords love thermos instead of clutch fans and its a good mod to do.

is there a big cooling diffrence?

As far as cooling, not really as they only turn on when needed, as far as freeing up 5 - 10 hp if not more then definately as the fans are stealing horsepower by being turned by the motor. And it kills that god awful noise. Its the first thing I do on any clutch fan equipped car.