Zach, go for row 15!!!!! While you wouldn't be "unhappy" downstairs, it just isn't the same as being upstairs. From my experiences upstairs vs down, the service upstairs tends to be better and the leg room in row 15 can't be beat! Also as mentioned above, less noise & less traffic.

FWIW, last month ORD-HKG, I stopped downstairs when I decided to go for a walk and chatted with a couple of the younger FAs who made a comment about how the UD is like being on a private plane. That was the 2nd or 3rd time I'd heard that although I'd never quite thought of that comparison myself.