The higher the intensity the better. Intensity means current (mA, or milliamps). Higher current penetrates deeper in the muscle tissue, thus recruiting more muscle fibers. Higher recruitment means helping more blood flowing in a larger portion of the muscle.
Because Active Recovery programs (like those in Globus and Compex machines) are made of twitches rather than sustained contractions, and twitches develop only about 1/3 to 1/4 of the force one develops with a sustained contraction, one doesn’t run the risk of overloading muscle fibers and the tendons, or to make them sore.
There are a couple of differences between the Globus and Compex Active Recovery, if anybody is interested.