This is something I'm pretty sure of:

Things I'm comfortable doing:

1. Submitting to a woman
2. Switching with a woman
3. Switching with a man
4. Dominating a man

It really depends on the personality of the other person: I know one woman that I simply cannot conceive of dominating, even though she's a submissive - so switching with her is out of the question, and so is submitting to her, so it's never going to happen. Otherwise, though, I generally prefer switching with the same person.