I have 5 betta girls in a community - that began with adding first 3, and then taking out the troublemakers and adding the others. Now all my bettas are together in there, and having the other community fish (in my case - the 3 cory's) - takes a lot of the territorial attitudes away.
Most of my bettas follow the corys around as they zip around the tank. I think at least my littlest betta believes she's a cory because she's imitating them. Very cute. :)
I think you should try the community tank - and make sure you monitor them to see that the bettas don't bully anyone, or similarly, they aren't surrounded and pestered. There's a chance you could get the right mix and have one really happy tank. :)
My tank has been only up for a week - and I only added the whole gang/with cories on Friday - but, it's really something experience a time when it's all working well.