I think, that you will even get more stutters in sli, because the higher fps draws to fast for textures, which have to be loaded up in the vram. Is the vram full, it hicks up even worse, because he do not have all information available in time.
Interesting to hear from a guy using crossfire/sli with 2 cards with 3gb vram each. I thinks, he would run very smooth in comparison to 2x 580's with only 1,5gb. Would be interesting!

A slower card with more vram could beat the 580 setup in running smooth and with sufficient fps.
Anyone here with 2.5 or better 3 gb cards?