Either would work. Can you adjust the flow of the filter? And the tetras may fin nip the betta depending on which kind you get.
1 male crowntail betta
6 neon tetras
1-2 nerite snails
Would look nice
The betta may or may not be aggressive towards the neons. Bettas are more territorial than aggressive, so you could pull it off if you have plenty of hiding places. I have a betta In my community tank and everything is fine, he doesn't bother anyone. He just minds his own business. It really all depends in the temperament of the betta.
I'd say go for It! It would make a beautiful tank!
Hope this helped