Ok, you are really asking about cadience. Theres a secret about it, that if you can spin like 100 rpm or more theres some power in there you would not have otherwise. Its a tradeoff of how to make power. N reps at a given force or 10xN reps at 1/10 the force. Its hard to describe, but you know the effect of a flywheel spinning at a high speed, and how its energy can be released, its using your legs in motion as a force instead of just the pushing force of the muscles at low speed. The ratio of slow twitch and fast twitch muscle you have will tell what works best for you.