Originally Posted by CrankyOne

This is a good point that I hadn't thought of. When I was racing we spent considerable time analyzing pedal stroke for power and efficiency and a gob of time training to use that info and develop good strokes. So for an average person (and I'd include me today) there may be little or no benefit.

Perhaps the best benefit is that the cleats force you to place your foot in the proper place on the pedal but that's easily done with flats as well.