First, most potentiostats are also called galvanostats, and there is just a single technique called cyclic voltammetry (CV) on them.

The idea of cyclic voltammetry is to ramp the potential of a working electrode in one direction and also in the opposite direction. In that case you measure the current at each potential. For galvanostats, it means you will vary currents to get potential. Both are two sides of a coin and can both achieve the same aim as far as I understand.