What are some alternatives?
When comparing SourceTree and Git Extensions, you can also consider the following products
GitHub Desktop - GitHub Desktop is a seamless way to contribute to projects on GitHub and GitHub Enterprise.
SmartGit - SmartGit is a front-end for the distributed version control system Git and runs on Windows, Mac OS...
GitKraken - The intuitive, fast, and beautiful cross-platform Git client.
git-cola - git-cola is a powerful GUI for git, a distributed revision control system.
TortoiseGit - TortoiseGit is an easy to use client for the Git distributed revision control system.
Atlassian Bitbucket Server - Atlassian Bitbucket Server is a scalable collaborative Git solution.