I tried a really cheap, years old RGB splitter that I had lying around, so I could connect multiple consoles to a single RGB port. The results were poor. Here's the comparison shots with my SNES RGB cable: As you can see, the colours are more washed out when using the splitter. Is there a good RGB splitter out there that doesn't do this?
If you can find a MadCatz SCART selector, grab it, though very difficult these days. http://www.videogameperfection.com/2011/11/23/scart-switch-roundup/
^^^it's a custom made one, but costs a fortune. hana switches are cheap and common and do a good job.
You said splitter but it sounds like you want a switch. I believe this is the one that retro is referencing: http://www.assemblergames.com/forums/showthread.php?52513-gscartsw-automatic-8-1-SCART-RGB-switch/