high rpm? high torque? high power output? high efficiency? long service life? the best looking? the best built?.......
There is no easy answer for yr question.
Basically, Yokomo based motors are designed by Mike Reedy ( a legend in R/C Motor ) and were build by Sagami in Japan. Sagami use the best TDK C4 magnets on the market which are better in terms of heat resistance and magnetic strength, therefore more reliable.
Infact, Sagami also make OEM motors for other companies as well (can't remember exactly which). I personally like the design of Yokomo based motor. Tamiya are the least expensive as I could remember. Furthermore, 23T are mass produced, so it's simply by LUCK and some tunning techniques.