Seat width on a 739=17.3 on a 747=17.0 on a 777 with 10 across=17.0. 777 will feel roomier due to the higher cabin height. The 739 at .3 more is NOT any better. Not in that little stretched fuselage.
These are going domestic not international (at the moment)
10 across 777 feels better than 9 across 787. I've done both.