git
Git has been the standard, it is more transparent in operations
then other source control systems and allows more flexibility in terms of
scipting and automating, logging etc. Git is also great for beginners
fostering a solid understanding of principals involved rather then
"black box" results. When things go wrong (and they will) you will have
the grounding nessesary to troubleshoot and deal with merge conflicts
and other low level issues. That being said, the terminology used in tools etc
is transferable to other systems.