The 737 FMC in a lot of respects is far more advanced than that of the 777. There are a number of useful function used often on the 737 that just aren't available on the 777.
On the 737 there is a temporary WP data base where user made waypoints are stored and deleted automatically upon landing. Unless I'm missing something, this is not an available feature on the 777 (the ones I operate anyway 777-300ER).