Can someone clue me in? What practical benefits will there be from having twice as much video RAM besides feeling good about having more video RAM?
The larger frame buffer means less swapping for textures in larger resolutions, especially in ultra-wide aspect ratios with more objects on the screen. And, especially with AA turned up. I showed this in my benchmark of the GTX 275 896MB and 1792MB cards. The overall average FPS in the Far Cry 2 benchmark didn't change, but there were far fewer hiccups and stuffers. This resulted in a smoother gameplay experience.
http://www.widescreengamingforum.com/wiki/WS_and_WTH_Benchmarking_(GTX_275)
These graphs in particular. Notice all the little dips with the 896MB card as it swaps out for new textures? That is a stutter.
Once I get my Eyefinity6 card to test, I will be able to do the same comparisons between the HD 5870 (which has 1GB) and the Eyefinity6 edition (which as 2GB). This should provide a good baseline for how the basically "HD 5870 CrossFireX on a card" HD 5970 will perform with increases in the frame buffer.