That's a very big hospital tank... Not a very big tank, but that's a lot of water to treat and you'd only use 1/4-1/2 of the tank if the fish couldn't swim well...
I'm torn between dividing and community. I have three 10 gallons: 1 community, 1 divided, and 1 that will be a community when I have my EE betta, but for now is home to just pygmy corydoras.
When I first tried dividing a tank, both bettas got stressed, which is when I tore it down and made it into a community tank with one betta. I've recently divided another tank to see if two new boys will like it.
Community tanks can also be stressful if not everyone gets along. I personally have had a lot of luck with corydoras in a tank with a betta, but not as much luck with neon tetras. I've heard a lot of people say their bettas do well with corydoras, but others did not.
Either way, it all depends on what personality your betta has, and how much time and effort (and money) you want to invest into this tank.