Only real difference in the C class is that the 767 is 2-2-2 seating and 777 is 2-4-2.
The 777 BF cabin is split into two, with two rows forward of the galley, making a fairly secluded section whilst the 767 is one cabin with five rows of seats. Both aircraft have forward and backward facing seating.
If you are flying overnight eastbound, 767 centre aisle is guaranteed that you won't be disturbed, and can move about freely. In both aircraft, if you are in the window seat or middle seats getting out when your neighbour has the seat fully flat is difficult without disturbing them.