I too race 23T here in Okinawa Japan, and just about everyone here is using a Yokomo 23T ST torque type motor with the "MAX" type endbell.
I had very good results (performance-wise) with a standard endbell 23T from G-Style, but I just picked an Extreme Hurricane XX (EXM-111) to try out this weekend. It's based on the Yokomo Max ST TQ type motor mentioned above, but 3D balanced.
We'll see how she does tomorrow...
Other than that, I've used G-Style, Yokomo, and Xenon. All have been pretty good, and all the torque type motors were in the same ball-park, with the balanced ones (Xenon) having just slightly more response. The RPM motors were definitely faster on the longest straights, but would heat up with the same gearing as the torque-type motors so many of them would not last a whole day. A fast motor that can't complete a day's racing just doesn't do me any good. I could gear down, but then I'm on the same page as everyone else using a torque type motor, but with less response. How fun is that?
It probably depends on the track layout as well. For our track, the torque type motors do best. I'm looking forward to trying out the Extreme Hurricane tomorrow.