I say get the 10 gallon, 1 male betta, and a shoal of 6 panda cories. The cories will be happy, and the betta will be lounging all day as his underlings scour the floor day and night.
By the way if you do get cories, do yourself and them a favor and get sand as your substrate. While standard gravel is suitable, they much prefer the soft sand over the potentially harmful gravel. Not to mention it's better for their underbellies, which will be touching the floor constantly.
You will also notice their barbules will grow to superior lengths compared to those who skim gravel all day. When I switched half of my tank to sand, my cories' barbules finally healed nicely and actually grew, compared to their often uneven, short, seemingly damaged barbules before. I'm not saying that gravel = bad, but would you rather have a nice soft carpet to walk on all day, or an uneven, bumpy floor?
Good luck!! I love small tanks!! :D :D :D