Last season at the Tri-Clone indoor track, I ran a couple of races in 4300 with the SS, and even though I never got the car handling quite right, I felt like I had just as much power/speed down the straight as anyone else. This year I ran the 4300 with a GTB a few times, and haven't noticed a difference in performance.
I'm now running my SS with a 13.5 motor in the Late Model class, and again, I don't think I'm lacking power off the turn or speed down the straight. My lap times are around 3.6, with a few high 3.5s thrown in. Like I said, I still need to work on the chassis more, but I'm happy with the ESC performance. I left mine stock with the heatsink and capacitor. It barely gets warm after a 100 lap race, around 6 minutes.