This is a great topic, Lisa and I have done both MMF and FFM. Lisa will tend to lean to the FFM, I myself do not care I have fun in both cases.
I must say that the last FFM we had was great the girls got out a strap on not only did each other but I was also fucked by both of them with the strap on. I find there is something about a woman with a strap on that turns me on big time.