I'm right-handed (with one exception*) and unclip right foot first. I don't think I ever consciously thought about it, just have always done it that way. I think it's because I like to push off the ground with my stronger leg (just like when I was little and rode a scooter ).

*[The exception is when I had to learn to do venipunctures, I taught myself to stick with my left hand so I wouldn't have to switch hands (and risk jiggling the needle) in order to swap out the tubes. Yes, an odd bit of trivia...]