In First/Business I prefer window. In coach, for flights under 2 hours, and if I'm not in a hurry to get off the plane, I'll do window. For flights more than 2 hours, I'll do aisle except on aircraft with big exit rows (i.e. 747, 777) in which case I'll take the window in the exit row. I like to look out the window (it's pretty much all I need to keep myself occupied even on a 14 hour flight).