Personally, I always opt for an aisle seat when I can. This is because I have *slightly* more room to stretch out and also because I'd rather have people climbing over me than have to climb over other people if I want to get out of my seat for some reason. To be honest, on a short flight it probably doesn't make a lot of difference, but on a longer flight it can.

Happily, though, not everyone thinks the same as I do and lots of people (possibly most) would prefer a window seat, for obvious reasons.

I guess middle is not so popular.