I think (in my limited experience) that yeah, their might be gender differences overall (on average / statistically), but that it really varies with individuals. My example, with my guy, Mal. Yeah, he's interested in a threesome, but honestly when it comes down to it what he wants is a mental and emotional connection with a third person. He grew up with a pretty rough life, I won't go in to details
, whereas I was very sheltered. There are a lot of things he can tell me that while I can sympathize with him, I really can't understand on any level. He wants someone he can talk to who can understand. That was the main draw for him towards Beth, the woman who almost-but-not-quite entered a triad with us - he felt that she could understand that side of him.
On the other side of it, yes, we have agreed to basically a one-penis policy - if I happen to fall for a guy, we'll talk about it and see from there what the best course of action is, but I'm not going to go looking for a guy. There's two reasons for this. One is the stereotypical. Mal had several girlfriends before me leave him for other guys, so he has a bad association. We've also talked and agreed that there's a cultural influence - culturally speaking, if a girl gets it on with a guy that isn't her husband, he's being "cock blocked" and she's probably going to leave him; but if she gets it on with another girl, that's just hot and means the girl's husband is probably going to get some. We don't agree with those stereotypes, but that doesn't mean they don't influence his feelings and insecurity. The other factor influencing our one-penis policy is from me, and goes against the stereotype of women being only into feelings: I'm bicurious / bisexual and never so much as kissed a girl, but I really want to explore that side of myself. So I'm really more into finding a female partner right now, and don't mind the one-penis policy.
Hope that complicated things lol