That's a pretty broad question. I consider dependability and efficiency to parts of performance.

I'm not trying to knock anyone's equipment, but I consider a MM/Feigao combo to be something that you run just until you can get something better. Where I am, the temps are just too high to get any sort of long running times with a Feigao motor.

If you are talking in terms of raw speed and torque, then I'll go out on a limb and say that a 7XL or 8XL on 4S will outperform a stock ST.