I would place them in the same category as monogamous heterosexual relationships. I think creating a delineation between heterosexual relationships and homosexual ones like your doing is a strange way to make a point. I also lived with a lesbian couple for a few years when I was younger. In my personal anecdotal experience, I like hanging out with lesbian couples more than gay male couples, but about as much as heterosexual couples. Granted, that’s my personal lived experience. I wouldn’t assume I’d get along better with either on average though. Mostly just the people I knew. Weird to create that divide considering an open relationship is in no way equivalent to a gay one. In fact, some open relationships are gay.