Originally Posted by
scottgir
A lower KV higher voltage set up is always more efficient than a high KV low voltage. So the 3000KV on 4S will be noticeably faster with more torque than the 6000KV on 2S. The 6000KV will lose more energy through heat than the 3000KV setup.
This is only true for the ESC, due to the I2R losses. The motors will have similar efficiencies and temperatures if they are of similar construction and power output.