What do you mean by "racer"?
For real racing the Fit is the better car as it makes a good B Spec car. Plus it's a manual.
Have you looked at the classing for the two cars in your series/class of choice? Look at the results for the last couple of championship years to see how competitive they are in class.
For autocross - no trans cooler is needed. But changing the fluids more often is not a bad idea (and/or using better synthetic fluids).