There are not many choices available for Unreal (if you use it inside the engine). I tried GitHub, SVN, SourceAnywhere, Plastic SCM, and Perforce. At the end I went with Perforce. I just cannot stand all those extra source control files and directories in every sub-directory of my project. Perforce keeps my project clean. Free for 5 people as well 
and it’s used in most game studios. What if I need more licenses? Well, I wish to have that problem.