If you are creating open source applications, there is almost no reason not to use GitHub. If you do need private repositories (for proprietary or private, business or personal use), Bitbucket could be an excellent solution. Beanstalk's main advantages lie in the support …
For business or personal applications, where you wish your code to remain private and/or proprietary, Beanstalk could be a good fit. If you are also interested in beginning to automate with relative ease, their tools can be a great help. Code reviews can also be a key factor in the decision, as they provide a good framework for accountability.
If you are creating open source applications, there is almost no reason not to use GitHub. If you do need private repositories (for proprietary or private, business or personal use), Bitbucket could be an excellent solution. Beanstalk's main advantages lie in the support (which is excellent), deployment tools, and code review features.