Are you talking about using SLI compliant RAM with 2 GPUs in SLI or just SLI RAM with one GPU, because either way, as far as I know, there arent really any significant advantages to using SLI compliant RAM over normal RAM. For the most part its just another sticker they can put on the box to catch attention and help raise sales, but is also going to make the RAM a little more expensive since they have to pay Nvidia for that qualification.
Yeah, the first one isnt anything special, just has a qualification from Nvidia (I have OCZ btw, and its been wokring great). The timings on the second are slightly slower, but the bus speed is faster. I dont know how that relates to real world performance though, and hopefully someone can come in here and tell you.