I'm sure there are probably some threads on this around somewhere.

I've only done a couple of return trips in J on a 777 and to be honest I'm not a great fan of it. The large expanse full of beds 2-4-2 config makes it look like a load of coffins. OK so its better than WT+ but out of preference the 747 is much better in CW.

The Upper Deck is great, 2-2 config, max of 20 people and two FAs so the service is always pretty good. IAD usually runs a 38 CW seat config (last time it was 70 CW seats) so the main deck is quite small although cosy is a better word. When I get a choice of flights to a destination offering 747 / 777 (eg. IAD) I always take the 747 regardless of cabin.