BitBucket is one of the largest code hosting solutions out there. Supported by Atlassian and used by millions, it uses both Git and Mercurial.
Ranked in these QuestionsQuestion Ranking
Pro Free unlimited private repositories for small teams
Bitbucket offers unlimited private repositories for free, as long as the number of members in a team is not larger than 5. BitBucket does not use GitHub's pricing plan, instead of charging users for each private repo, it charges teams per number of team members. It is free for up to 5 people.
Pro Supports both Mercurial and Git
Has full support for both Mercurial and Git VCS.
Pro Native application for both Mac and Windows
Atlassian, the company behind BitBucket is also behind SourceTree, a free application for Windows and Mac wich works as a client for both Git and Mercurial which can be connected to BitBucket and other code hosting services.
Pro Multiple authentication methods
BitBucket supports GitHub, Twitter, Facebook, OpenID, Google and even GitHub authentication.
Con The UI seems old and not very polished
While GitHub's UI is extremely simple to understand and very polished, BitBucket lacks a bit on this category. With a design that seems old and not as pleasant to look at.
Con Only 5 users are free
5 users free: Unlimited private repos, Dedicated support, Code reviews, Custom domains, JIRA integration, REST API.
Con Integration with other tools is not as good as github
Most of the 3rd party tools ( bug trackers, CI servers, chat servers, etc) always integrate with GitHub first, and either don't integrate with Bitbucket at all or do sub par job in it. For example there are 3 separate projects to allow building and verifying pull request submissions on Jenkins CI server and there is only one viable one for BitBucket and that one is really buggy and lacking many features.
The only exception to this rule is Atlassian products like Jira.