Hi there
I know every fish is different, but I have kept several males (one at a time) with groups of females (6-9) in a 50 L tank over the last few years. There is never a problem between the male and the girlies. A couple of the girls pick on each other for dominance, but only of the female social ladder. The male, upon introduction, will chase the girlies and flare excitedly for the first day, but will lose interest when he realises the females have none. I have bred the males with one of the females successfully a few times. Upon putting him into the breeding tank and introducing one of the females the next day, both are very eager to breed. I dont know if its because they miss each other after the day or two or because there are no other females around to spoil the fun (other females will not let one of their own breed with the male - jealousy I presume). However, an aggressive male might not ever let the girl(s) alone, some people may vouch for that, I just have not seen it. A sex-mixed tank has always worked for me. In saying that I have seen some nasty Betta females, that I had to return to petstores, as they constantly rampaged trying to KILL the male and females.
So my short answer is, it works for me but it depends on the temperament of the actual fish.
LEE