I just had my third lesson Jiu Jitsu, and I am learning some basic throws right now. From my own experience, I can say that the smaller guys had trouble performing a hip-throw with me, because they couldn't get my legs of the ground. I am 6 foot 5, so that was a small advantage for me. Still, I don't think size matters, nore does weight or strength. If you apply a technique right, everybody will fall or be barred, no matter what size, weight or strength they have.