When my wife and I travel by plane, no matter who books the tickets, I sit in the middle. (We have a not-nice name for this spot, which starts with a 'b.') Depending how my wife's mood aligns with the airline's available stock, she might nab a sweet window seat -- all the better for balling up her jacket and leaning her head in a modicum of kinked comfort; or she might rock the aisle, able to sit or stand (almost) at her pleasure.
So then, what's the best seat for me? Next to her, obviously.