I prefer the UA
777 if I have to fly coach, partially because of the PTV but also because the seats are 18" wide versus the 17.5" seats on the 744. The Business class seats are about the same and the 777 First beds are supposed to be slightly wider but I have flown in both and never noticed the difference.
The 777 is truly miserable if you are trapped in the middle seat, requiring a "double excuse me" to get to the aisle and no window. The 777 might also be slightly quieter, but it may have been my imagination or related to the position of my seat.
In Coach, my first choice on UA
is actually a 767 because it has few middle seats, so you are likely to get either a window or an aisle. They also have 18" wide seats and PTV.
Don't forget to check http://www.SeatGuru.com
I still miss the pre-deregulation 747s with only 9 seats abreast and lounge areas in the upper deck and back. I flew on a domestic 747 back in the golden age that had an organ or piano in back and a sofa like seating area, on Continental, I think.