It depends
I can't pin this one down.
Sometimes Window, sometimes aisle. For years I flew exclusively aisle. Then about 4 years ago I started taking windows on occasion. Now I waffle between window and aisle. For Redeyes, windows are my preference as well so I can lean up against the hull and sleep. Otherwise, I usually take an aisle so I can get up, and stretch out more, without anything next to me on one side.