Would a 9l work in a revo?

The XL motors are longer, so there's more area to dissipate heat with. Because of this, 90amps through a XL motor will keep it cooler than 90amps through a L motor. Having a XL motor run at the same temp. as a L motor will cause the ESC to heat up more because the XL is pulling more current.

This is true technically, but you wont see any significant heat loss front the larger can because of surface area. The XL runs cooler because it draws less current because its running much lower RPM. Its like taking a 700cubic inch motor to move something a 350ci will move...the 700ci work less for same result. You do have a larger surface area, but a larger heat generator for the same token. Its similar to compare the 9L to a 15L, the 15L has more torque and doesnt work as hard...needs more voltage(as do the XL's). More voltage= less amps....less amps= less heat.