50 gallon or 15 gallon for sorority?

[auroraeyes]

I just scored insane guys!!
I purchased a 55gal tank with all it's accessories off craigslist for $40!!!!:D And the extras(decorations, light, filter, back up filter, heater, thermometer) weren't exactly cheap either. The guy knew what he was doing, had the proper filtration and heater, the heater itself is worth more than what I paid for the entire setup.
I'm absolutely ecstatic!
I'm going to clean it all up tomorrow and start cycling it right away.
I'm getting 5 female bettas from another member on here(otter) in a little bit who can't keep them anymore, and I had some questions about sorority recommendations.
I currently have a cycled 20gal with some tiger barbs, I just began stocking it when I responded to the craigslist ad.
Do you guys think it would be a better idea to:
a. Set the girls up in the 20gal by themselves and stock the 55gal separately
b. Set the girls up in the 55gal and add more females (maybe have 10-13 altogether)
c. Set the girls up in the 55gal and add different tankmates.

Any advice on sorority decorations good hiding places is also welcome, I've been reading a lot about them in preparation but I've only ever kept bettas alone.
I'll be sure to post pictures once everything is set up!

[Sena Hansler]

Really depends on what you want. I like using larger tanks, since not only can the females get along better, but you can decorate it to its fullest plus add tankmates if you so desired. I always find the more space the better ;)