If it works then it's probably the right device. Typically for a transistor used as a switch your main concern is it's on/ off frequency response and then if it will withstand the operating voltages and currents. If your concerned about power dissipation and not so much about frequency (switching a motor is low frequency) i.e. battery operation I would think about using the Mosfets.
Ideal conditions you want are as follows minimum transistor turn-on current and voltage (base to emitter current for NPN). Near zero voltage drop across the transistor (Coll to Emitter volt.) when transistor is saturated. Zero current flow when transistor is OFF. All within your frequency (Bandwidth) of your application.
I can go on and on.