You want to look at Watts, RPM and Torque in that order in the 15 to 25 amp range. The most important measurement is the 20A wattage number....the higher the better.
Don't bother looking at any readings over 30 amps. Stock motors do no operate in this range on the track. The motor with the most power in the 15-25A range will be fastest on the track even if it has a lower max power reading than another motor at say 30 or 35 amps.
What I run: Schumacher Mi5/Associated RC10R5.1/Associated RC12R5.2/Futaba/HobbyWing/Team EA Motorsports/BSR Racing
Where I run: Florida Indoor R/C Complex/Thunder Racing/Florida On Road State Series