Always the window
1) Gives you a place to rest your head.
2) The view. There are literally billions of people on the planet earth who will never get to see the earth from 30,000 feet. To look down on cities, mountains, landmarks, oceans - It's a treat that should never be taken for granted.
To wit -
http://flickr.com/photos/geoff_ana-maria/2912844719/
http://flickr.com/photos/geoff_ana-maria/1477951204/
http://flickr.com/photos/geoff_ana-maria/123776188/