For the A380 in Y I'd be going for the window seats at the back of the upper deck. The side bins and the extra lateral space that you get as a result of the sloping cabin walls make a pretty big difference. It's a smaller cabin, too, making it rather easier to get crew attention.

For my money, the spacious feeling, while nice in an empty cabin, doesn't really make up for the extra noise that comes with it on even moderate loads.