Generally, you want both a gyroscope and an accelerometer, as they measure different things.
There are lots of affordable, high-quality solutions on the market now, because of MEMS sensing technology where you basically build the sensors as part of an IC.
You may even get a 9-DOF system (3 DOF gyro, 3 DOF accel, 3 DOF compass) for the same price. Although I think the compass wouldn't be that useful for your application, and would be confused if you have lots of steel/motors in your device.