Personally I find the lower pressure of the 787 makes for a much more pleasant flight. Less dryness, plus it's a newer plane, generally better condition and less chance of random breakages. Depending upon your flight time the crew can (will) also control the shades, which I tend to prefer.

You should also get access to the rear J washrooms on the 787 if you were to go for PY, which you won't get on at least the 77W. They aren't exactly stocked with stuff (I think they have moisturizer but no toothbrushes or razors for example) but it's a much shorter queue.