For 17.5 non-timing 12th scale, my top 2 choices would be the Revtech and the Reedy Sonic. Both are very quick, have a huge range of timing adjustment, a good selection of tuning rotors available, etc. The Sonic runs a little cooler, is a bit smoother, and has a bit less fade over the course of an 8min run. However, throughout my testing I have found that the Revtech generally yields quicker outright laps in the first 90-120 seconds. In regards to which motor is the best, it's a toss up... both are great motors. At this point I feel more comfortable with the Revtech as I have tested substantially more rollout/timing/rotor configs.
However, I have not tried the Thunder Power motor and would very much like to. I have heard and seen very good things...