Following are the features that Bitbucket provide with all the plan
1. Unlimited private repos
2. Dedicated support
3. Code reviews
4. Custom domains
5. JIRA integration
6. REST API
Bitbucket has an advantage over Github as it offers free accounts with an unlimited number of private repositories. These private repo can have up to five users in the case of free accounts and if you invite 3 users to join Bitbucket then you can add 3 more users which make the total of 8. By this Bitbucket gains an advantage over Github.
If you are a team of 8 people or less developing a project and want to make use of some private online repository, then, Bitbucket suits you.
And if team size increases then you can go for different plans. See list of plans