So I realized that since I don't have Pudge yet, I can't be 100% sure the divided tank will work out. There will be about 1-2 inches of space between them (there will be a filter and heater between the dividers), but there is still a chance of one or both of the fish getting stressed from having a tank mate.
Now, I'm not saying this will happen. There is only a 10-20% chance of me attempting this, but what fish could go in a 5.5 gallon with ONE betta?
I'd be leaving the nicer one in there if there is any hostility between the bettas, but I'm just curious if things go sour.