747 upper is good, more private as people have said but the storage shouldn't be overlooked - you can't fit a roller in the overhead bin, or a good size rucksack, meaning they'll be in a closet which the FAs are very unhappy about you accessing during the flight. Again, if you're on the window seat you'll have storage between you and the window, but only a small roller or backpack will fit.

One note on a recent flight 747 upper deck - the bathrooms at the front of the cabin were blocked off by a wire curtain so passengers could not access. This meant that the whole of business class was sharing the two bathrooms on the lower deck and from the upper deck, you had to walk downstairs with no indication of whether the bathrooms were vacant. That was annoying.

Experience it once, sure, but the 747s are on their last legs and if you can be in the window on the 777, I'd argue it's better.