777 seats have more room than 747's due to the fuselage shape. Right behind and outboard of CA there's a bin that F/A's can sit on. 747 is too pinched for that.

777 center j/s seems to have fractionally less legroom vs the 767 but the seat itself is better(vertical adjustment, etc).

Fourth 777 j/s is for truants. They're stuck off in the corner by themselves.

777 is also quieter than early model 747's that I j/s'd on.