Which is better? (mega/feigao)

[speed demon]

Well my mega motor came in today. I put it on and its not working right. Just holding it in my hand the motor kicks hard and no cogging what so ever but it seems to not be getting max rpm. Holding the motor in my hand the rpms climb fast but it seems to be lose power then power comes back really fast back and forth. The motor barely gets warm and the speed control, bat and wires are all cool. Any suggestions? If its the speed control what one would you guys recommend?