overpower

[RC-Monster Mike]

For sure the 7xl has higher torque. Be careful if you over cell these motors. If it draws too much power, it will damage your speed controller. The 8L could handle some high voltage for a bit, but it is far from ideal. If you want the power of 20 cells, get a motor that can handle it(as sguee mentioned, the 8xl or even better, the 9xl).