In coach:
Window on short hops for the view, aisle always for longhauls. I like to stand up and stretch or use the bathroom every few hours and it's nice to be able to do it without disturbing the bloke next to me. You can also stretch into the aisle if really desperate as well.

In Premium Economy:
Only flew the QANTAS version but same as coach.

Business/First:
There's so much space that I don't care where in the cabin I'm seated. Window preference here for the view.