Although I prefer F in the 747 I think it's very marginal. Being in the nose of a 747 is something you must do once (if you're into trying different stuff/experiences) but apart from that there is very very little between the two.

Certainly if I was booking anything now I'd be primarily deciding on destination/date/time before adding 747 vs. 777 as part of my decision criteria.

Different story in J - 747 every time!! (Unless upper deck not available or it is 3-class 777)