I would say size most defintitely matters. One of the guys at my
class, is skinny, tall, and has the longest freaking arms I've
seen in my life, like a freaking ape long ^_^ Another of the
guys is huge, I mean like biceps the size of my thighs huge ^_^
Certain things work on bigger guys, certain things work on
smaller guys. So yes, size makes a huge difference. One doesn't
go the inside of a bigger guy unless you know exactly what the
heck you're doing there. That's why I normally stay the outside,
because I'm smaller than most. However, I don't think this
pertains to who will win or not. The size and the strength that
comes with it has to be applied through form. In my humble
opinion, I'd say a small fast guy that knows a small fast guy
form would be about even with a big strong guy that knows a big
strong guy form, at the same training level. That may just be
hope talking though ^_^