Single Card vs. SLI

I am sure this has been asked about 1000 times, but looking at getting a new M17x (or possibly upgrading the older one) and looking at either 2GB Nvidia 680M or dual 680Ms in SLI formation. Is there really an advantage to SLI? I've had the Radeon Crossfire setup in my current rig and it's caused no end of driver updating issues. Suggestions?