On this route I would be inclined to book on the basis of schedule and catch one of the later flights out of NYC to ensure that I am ready for bed after take-off. I would probably choose the last flight out of EWR.

If there is a choice of aircraft and having experienced both 747 and 777 on a similar run (BAH-LHR) I would prefer the 777 as I always seem to sleep better on this aircraft.

I think that the air quality might be better on 777 vs. 747. The cabins are certainly in better condition.

There are also complaints on this board about the 747 being very hot, although I have not experienced this myself.

Go for a window seat on the 777 for superb privacy. I prefer row 13 since this is the only row guaranteed a full complement of windows.

Whichever flight you choose, I hope that you sleep well!

And I have one final recommendation: wear the ear plugs and eyeshade to avoid any announcements or ambient light and choose to get more sleep instead of eating breakfast.