I don't consider myself any kind of martial artist. I have trained for a few years, and I enjoy it, but I will be the first to admit that I don't know much.
But come on now. Size does matter. If the size is all they have, and they have no skill, or drive, or will then it probably doesn't matter. But if you put 2 fighters of equal skill and one of them weighs an extra 50 pounds, he will probably win.
My teacher used to say that the scariest thing you could fight were either very big men, or very fast men, but the scariest thing that you could ever fight was a fast big man.
-Larry Correia
Big & Slow