On international longhauls my preferred seat is a bulkhead aisle - and in business class if I can get it . This allows me to get up and walk around. Also, there is no seat in front to lean into mine. On USA transcons I am not that choosy, but I will usually take an aisle. On European shorthauls, it is always a window. I love viewing all the different airlines and airplanes at LHR, CDG, FRA, etc.