I think I'd have to go with grappling, because you don't have to be trained in striking in order to knock somebody out. It helps obviously, but it isn't a must. Whereas if you go to the ground with no training your in no mans land. You might as well be Art Jimmerson with one boxing glove on.
P.S. sorry if i got the guys name wrong, i'm thinking of UFC 1 when Royce takes the boxer down, and he taps before Royce can do anything to him.