I'm not sure I can pick one over the other.
With women, I love when they sit on my face. Just no gap between my face and their pussy. I also like when they are on their back. Some women will involuntarily put their legs and feet on my back and try to pull my face into their pussy.
With men, I love when their cock is in my mouth and I can feel it get slightly harder as a result of what I'm doing to them. In addition, I love when they involuntarily arch their back or buck their hips. And, yes, I will admit....... there are times when I love having my face fucked by a guy.