SourceTree is a desktop client for DVCSs in general, not a webapp, so I'm not sure of the comparison. It's a pretty sweet piece of kit regardless.
It's also a side-project of Steve Streeting, the founder of OGRE3D: http://www.ogre3d.org/about/team
It's also a side-project of Steve Streeting, the founder of OGRE3D: http://www.ogre3d.org/about/team