Ive run several different 17.5 motors, and If you want the best 17.5 motor then the speed passion MMM is the best way to go, but the motor has set timing built into the sensor board, so you have to switch the boards out to adjust the timing. The revtech is a great motor but has a lot of timing already built into the motor and runs hot if you turn the can timing up.

My personal recommendation is the reedy sonic. It runs cool throughout the motor timing range. It's the motor I run in my ft SC10, set to 42 degrees can timing and geared 28/75. After a 5 min qualifier or main the motor is about 145-150 degrees. I run in an indoor clay track with a 110+ foot straight.