Everything I've seen shows zero benefit to the larger memory SKUs compared to the standard ones. They run out of rendering gas before lack of VRAM becomes a major issue.
Cheers. I would've thought the 660 Ti would've had enough grunt to make use to the 3GB. I could only find one review of the setup in SLI when i was doing a bit of quick rewding on it http://www.hardocp.com/article/2012/10/31/galaxy_geforce_gtx_660_ti_gc_3gb_sli_review/#.UVS2PbQgGSM
660 Ti seems a bit strange then if the 2GB version can only really make use of 1.5GB properly and the 3GB isn't fully utilised due to a lack of processing power.
alright, ordered an evga gtx 690 to spruce this thing up
If money was no object I would've went for a Titan.