I would say that while it "might" be possible to put a male and female together, it's exessively dangerous. I know my girl Uta can kill my male Sori with great ease. She's not weighted down by a tail, she's very fast and muscley, she's highly territiroial (I think she killed a couple of my cories), and she's twice his size.
I had a 10 gallon that I went through the same waffley decision making your going through. I wound up putting 1 female betta in there with 1 otto and 3 ADFs. At the time, my female wasn't quite territorial yet, but she did eventually begin to attack my frogs. However, during the 3 months I had that setup, I found it to be quite peaceful and interesting. It was densely planted, very nook-ish, and stable.
I thought briefly of making it a sorority tank as well, but after many google and fourm searches, decided that I didn't want to go through the stress of trying to find a mix of females who won't cause each other undue injury.
Some people really like active, active, active! tanks. I find those tanks sort of dizzying to some degree. I enjoy having a focal point, so for me, the 1 betta solution was best.
Just decide on what you find aestheticallyl pleasing, figure on the risks, and fly with it.
