No data other than anecdotal but totally agree. I use flats on my road bike and look like an idiot but I go just as fast. I prefer to be able to wear normal shoes so I have less to carry. The whole "you can push while you pull" thing makes no sense, my quads are way more powerful than my hamstrings and you never need that much force when pedalling anyway, cardio fitness is always the limiting factor for me, not leg strength/power.