Personally I would go for the 777 as it is 2-2-2 as opposed to 2-3-2 across on the 773 so a little bit more space and also the departure time is much nicer 4pm as opposed to 1am for the 773 flight. Also the 773 flight has a habit of getting in early as I think BKKROP has mentioned before and the lounge does not open until 6am?