FilmSim = Firing two guns while jumping through the air.
MILSIM = Someone giving you the gears because you've got the wrong shoelaces for a US Army Ranger, or have 68 round mags instead of 30s.
I like to go back and forth between the two spots myself.
A real hardcore milsimer would turn purple at some of the stuff that passes on the field, and the casual players feel eight inches tall when they show up.
Airsoft, where nothing is hurt but feelings.