1. Your spring- how big is it? Is it over a M120? Or is it under? A good high speed motor like SHS or “Matrix” will handle
a M130 even with low voltage but a high torque will do it with no trigger lag and no “wind up”.
2. Power source – If you have or use a 11.1V lipo, NO high speed motor! It will sound awesome and throw bullets out that will scare all your friends. But alas your AEG will eat gears and pistons every time you use it unless you have deep pockets and and no girlfriend. I recommend a 9.6V NiMih MAX with a high speed motor and if your spring is under a M120. High torque motors are amp hogs but the only way to go with a LiPo. Even low tension springs work well with a LiPo in the 11.1V camp or really any voltage.
3. Semi-auto or mostly full-auto? A high speed motor is very efficient with juice on the O-scope compared to a high torque. The cost? It’s an inductive phase that lasts 4 times longer than a high torque on average. That means semi-auto will burn it up very fast. Often in one game too. If you do not shoot full auto all the
time stay away from a high speed motor. A high torque has little problem on semi all the time. It will get hot, but not hot enough to hurt it.
4. Why do I need a high anything motor? Often for the average Airsofter a stock motor is a great mid-level motor. It can do a little of both, and just like most stock motors they are good enough to pass muster. However a good high torque motor will breath new life into any AEG. It’s the soul of your gun really. It’s not a purchase you will regret ( unless you get a Guarder high speed).