To me, the 4000kv and higher motors are for racing, where you are 2s limited. For bashing, my .02 is to get the lower KV, then add volts to get more speed.
For the same end top speed, total power, with the same motor size, a 3s system will run cooler with longer battery life vs a 2s system.
For the same end top speed, total power, with the same motor size, a 3s system will run cooler with longer battery life vs a 2s system.