It isn't just VRAM use. It's the performance hit for 8X vs 2X for me. I'd rather use 2X for way more performance and 99% of the visuals. Like I said though, it's all in the eye of the beholder. I won't say either way is right or wrong, everyone has their preference. That's the beauty of PC gaming. Take your pick on what you like for image quality.
Oh yeah. I can't notice a difference between 2X MSAA and 8X MSAA. So then the question becomes, why am I using 8X MSAA on a 1600p IPS panel when it looks identical to 2X MSAA? Am I using it just because? For psychological benefits? And why am I taking a 30% performance hit for 8X when it looks identical? Just my line of thinking. But, It's all personal preference. Take your pick between performance hit and VRAM use.
I should clarify. I used 680 sli for ages at 1600p and even 8X MSAA was a non issue aside from te performance hit. Never had VRAM problems except at triple 1600p. At 7680*1600, yes, you want 6GB. Or 4k resolution? 6GB can make sense since you can use more AA with 6GB. 5760*1080 was fine even with 2GB, although you can't go overboard with SSAA there with 2-3GB.
But the bottom line is this. Anti aliasing is the biggest thing chewing up VRAM, so if you're using surround, more VRAM lets you use more anti aliasing, essentially. Does that matter to you? It's up to the buyer to decide really. Personally i'm good with 3GB because I don't go for 8X MSAA or 8X SGSSAA. Mainly because the performance hit for those settings is retarded when you consider 2X MSAA looks 99.9% as good as 8X. Even 3GB is fine at 4k resolution unless you use too much AA. If you use 8X SSAA in everything? Yeah, then 6GB makes sense. I DUNNO ABOUT THE 90% performance hit for 8X SSAA though. Or the 30-40% hit for 8X MSAA. You could of course throw more GPUs at the problem just so you can use more AA, and then get 6GB on top of that.Edited by xoleras - 3/24/14 at 6:26am