A person used to have a pretty good chance to get a whole empty row in the rear, and that was one reason to sit there. But with planes getting ever more full, I think it's becoming less common to have extra seats.

If I am in Y, my preference is to sit as far forward as possible. This is most critical, of course, if I have a close connection. But even if I don't, I'd much rather get into the airport lounge than stand in the plane aisle any more than I have to....