As a sub i think it's nice to be the physically weaker in the relationship. However, it certainly isn't necessary. And even if my Master is way stronger than me, i still could outrun him easily.
So if i stay with him, it's only because that's what i want to do, not because of his strength.

And the question that arises from this is...how or how much do you use your physical strength to your advantage and or as your dominance tool?
He uses his strength often, to pin me down and tying me and i just love it. Or he uses it to pin me down and tickle me, which i don't love at all *grrrr*