I cannot speak from the submissive side, but from the dominant perspective, it has been my experience that such activities tend to keep their power and affect on the submissive. Of course everyone is different and nothing is the same for everyone. I can say that the act of taking a slave anally is a very powerful act for me, and has most often lead her to feeling possessed and taken in a way that many other activities just don't quite measure up. I think there is an inherent submissiveness to offering oneself that way, and I know as a dominant, I feel particularly dominant taking a slave that way.

Not really what you asked for, but figured I'd throw my 2 cents in anyway.

D