Hi Phil
The Evo has a lot more power handling ability the the regular motor. You can use the small controller with the Evo but you need to be much more careful about cooling and other variables. With the 80A controller it is a much safer system with the Evo.
The "A" version controllers have the aerobatic brake on them. They are proportional if you setup your throttle that way. Essentially at a certain point in the throttle travel (which you can adjust with sub-trims/throttle curves etc.) the motor will start braking, and the further you pull the stick the more brake you have. Personally I set up my airplane with a low idle, and have a switch which lowers the throttle curve and gives me maximum brake which I use for only certain manuvers.
Hope that at least starts to explain it
