I have to say aisle.

I just like the knowledge that I am in control of when I want to get up,and not have to worry that I am being rude to the person next to me by crossing over them when I need to get up.

Also, I commute at least once a week LAX to SJC,and I want to get up and out (or at least standing up w/out hitting my head on the overhead bins) as soon as possible.

Just knowing that I can get up and get into my bag in the overhead bin, or go to the restroom, or walk the aisle when I want means aisles for me.