There is a big differance in the models but from my own reserch this is basically the strength and speed of the motor, some think and i agree that the batteries also play a big part,
Almost all of them have the same parts inside so it may be wroth buying cheap and then replacing the motor and batteries,
They do work and work quite well for a locksmith, there is no need at all for a hobby picker to have one,
They arent magic tools and do need some practice,