The :MP is made by a different team as the MTA. They are two groups (I believe the :MP guys are a spin-off from MTA) who have their own ideas and clients. For VC MTA was the first and still is great. For SA the MP group has the best client.
:MP has a VC server and client, but it is not used a lot and still not stable.
MTA has only a race mode, the DM/RPG mode is advertised a long time but has yet to appear.