I get variants on of this question from a lot of people actually, because the assumption is that, in these stories, I must Mary Sue myself into either the submissive or dominant position, when in fact my own interest in these stories is a bit more removed.
I have no real interest in being a character in these stories–my enjoyment is a bit more…voyeuristic. I enjoy the authorial perspective, and power. I like the fact that I can force these characters to undergo these changes, and that’s where my erotic thrill comes from. I suppose it would lean towards the dominant side of the equation, but I never really see it that way (and when I do imagine myself in these stories, I usually end up in the submissive position, so who really knows).