Had several MFF. It's obvious but highly depends on the vibe of all the people. In one case my girlfriend and I took home a girl and started out pretty fun but my girlfriend got unexpectedly abusive out of nowhere. I felt like I had to spend so much time keeping her in check and preventing her from going overboard. Another time one of the girls kept making weird awkward comments the entire time kind of ruining the vibe, you have to put a lot of effort into managing, which takes alot of the fun away.

In general it's interesting as a one off experience but I would always rather 1 on 1. There is enough going on with one girl and it's not like you can stick your dick into girls at the same time so...