Definitely window - for 2 reasons: for the view and leaning room/extra headrest. I too never tire of some of the views, especially into PDX and some of the Denver routes. I'm always up for a great sunset too.

I'm even more picky - window on the left side, anything but the bulkhead (bulkhead on shuttle seems to be growing smaller every flight). 2A if I can get it (and the upgrade, that is...)