I just used a 1TB WD passport (USB powered USB2/3) for my games after my 1TB seagate (powered) was acting sketchy, and without taking up another plug socket!
External is the simplest way imho, as my Laptop/router has never seen eye to eye with my PS3 to copy games to the internal drive.
I have a 250GB PS3 with movies, the odd game that requires internal, and game patches on, an external 1TB for games, a 750GB external for movies, TV series, music etc, and a 16GB stick for quick copying files to test or watch an episode or movie or something quick.
That for me is the best set up as I'm not moving my PS3 around.
But: If I were moving it around a lot, I would have my internal space maxed out, and not have anything hanging out the front bar the 16gb stick.
Yes mM can play split games, but tbh not many games are that big anymore