The intention of this forum is to answer a question that was in the middle of productive discussion until it was wrongfully deleted. I myself am giving my vote of confidence that a helpful discussion will endure by strictly posting things that I think are helpful to solving this issue.
Building off of this, sid, the toxic and vapor x have 6gb versions so that advantage would actually go to them although 4gb is likely enough even for 3 monitor resolutions. Unfortunately no benchmarks exist between the two as you would need a triple 1600p monitor setup with lots of mods and AA to max out 4 or 6 gb.
The issue that personally worries me more is if the smaller memory bandwidth of the 680 is enough to make use of all 4gb effectively.
I read a forum that said workstation gpu's are the same hardware just with highly optimized CAD abilities that are absent in gaming GPU's Is this not true? Can I get a link?
I would prefer the focus of this conversation remain on consumer cards that work with games though.
For the most part, this is true of "pro grade" GPUs. Also, the drivers for these devices are optimized for pro use. With these devices, accuracy (for example) trumps raw performance (like when gaming).