A380 is a great plane, very fun to fly on. Too bad they're being grounded on most airlines for the foreseeable future due to their economics.
The airline matters too - some have larger seats with more amenities and more space between rows. Those extra inches really matter on long haul flights for those of us who are tall!
I thought the air was less dry too, but didn't really have means to measure that.
My favorite plane for long distance is the 787. The mechanical bits are pretty noisy on climb out, but when cruising it's a really comfortable ride.
I like that actually; makes me sleep better. But the 787 is nice too.
Also it’s unlikely to have been upper deck gray water. More likely it was condensate.