Synchronizing game state - RPCs vs Sockets

Before I invest time into a synchronization exercise for, say, an FPS or an RTS, are Unity's C# RPCs light-weight enough to handle this?

For turn-based things and other things that are not terribly timing dependent, I can see RPCs being a great simplification and have done that before, but for something that runs in real time, if RPCs are slower, it may be an issue over the long-term for larger, timing-dependent games.

So, does anyone know/have sources regarding as to whether RPCs are better or worse than sockets for real time things?

Also, are either RPCs or sockets guaranteed to have their sent packets received or can packets go missing and do we have to prepare for this?