We've used both Github and Beanstalkapp.com and both charge based on total repos rather then disk space or developers which, frankly, drives me a bit insane. I think both have better features then bitbucket (as far as I am aware) and better UI's (subjective) but my 60 small repos run me $100/month at beanstalk - not sure what it would run @ github.
I can't find any disk usage limits @ BB's site, which makes me wonder if there are hidden caps. If BB ever struck me as being as slick as github, I'd move our business in a second, even if the cost was higher then it is now ($10 a month? Really?!).