Having experienced A380, 781 and 77W with new F seat they all seem to have +'s and -'s so there isn't one standout for me. I'm lucky enough to sleep well in all of them but the 781 is a more modern aircraft so as others have said has benefits from that. I do find the A380 feels more spacious as a seat and a cabin. While I haven't measured them the aisles seem wider and the seat area more spacious. With the 781 (and 777W) the look and feel is more contemporary and the IFE feels a generation or perhaps 2 newer.

The real make or break for me is the inflight service which certainly has come on this year but can be a little inconsistent around the edges on occasion.