I think most regular F travellers will say that the 747 is better by a mile. It is an absolute haven of tranquillity as it is in a dead end cabin. Nobody walks through the F cabin en route to elsewhere only if they need to be there.

The 777 F cabin is a through passage to the cockpit and the F Galley, so there is a "constant" flow of crew from rear areas to the front galley.

Even on a night flight there is always traffic to the front of the aircraft, whereas the only traffic on a 747 is PAX who need to go to the loo!

If you have a choice pick the 747. If you are forced to travel on a 777 do not sit on the left, as the left aisle is the one most commonly used by the crew.