Pega Robotics does not recommend a specific source control system over another. I have had customer use both GIT and TFS. Personally, I prefer SVN as that is what I have had the most experience with. The one challenge with any source control system will be locking files to prevent merging. Pega Robotics does not support file merging, so if you and a colleague both edit the same adapter and check-in your changes, your source control should be set to prevent those from merging the changes together.
In SVN, I request a lock before I edit any of the solution or project files. Once complete, I check-in and release the lock(s). If any of my colleagues were to try to lock or check-in any of the same files, they would be prevented from doing so.
In most cases, this isn't an issue as we segregate developers by application; which we separate into different projects. This allows developers to work on an entire project on their own before another developer uses each of those projects in a "controller" project.