My company is currently debating between Github and Bitbucket. And the funny thing is git vs hg wasn't really an issue. We've decided that either is so much better than svn that we'd take either.

We have 2 large road blocks for Bitbucket. First is a real nice review system with inline comments during a pull request. Is this coming soon? It's an absolute deal breaker for us.

Also the performance/usability seems to be lacking compared to Github. I hope that changes. Although we also use JiraStudio and it's performance is dreadful. And the usability is quite frustrating. So the Atlassian track record is a little worrying for us.