I always go for an aisle seat, especially on a long-haul flight, because there's frankly not much to see out of the window for most of the flight and I'd rather have easy access out and have someone climbing over me occasionally than have to climb over someone to get out. The only exception is when I have an exit-row seat with plenty of leg room, and even then I'm nervous in case someone's got the configuration of the plane mixed up when I book!