I am astounded by the Dylan’s findings in the video below, but he does cover some of the nuance that keeps me on clipless pedals. There is one thing that he didn’t mention though – connectedness to the bike.
There’s value, at least to me, in feeling connected to the bike. I know my foot isn’t going to slip off when I press down on the opposite side when screaming through a corner. I can be lazy when doing a bunny hop. And, perhaps more importantly, I’m much more comfortable riding in a wider range of cadences with a clipless pedal than on flats – I can’t do 120rpm on a flat.
Efficiency is important, and as he notes, it would be very interesting for someone to do a more thorough study into more varied pedaling applications to get a better understanding of where the differences are. Very interesting stuff.