Why GFX card with more RAM?

[SEE]

To help others and myself, maybe someone with technical understanding can help others and I regards the selection of GFX cards and the question of on board RAM. Please, could posters consider the future optimisation of the engine rather than its current format.

(Maybe the mods will leave this in the general forum before transferring the thread to Technical.)

Most of the reviews regards 2gb v 1GB seem to suggest that the benefits are mainly seen when using Higher Resolutions than 1920 x 1080 and very few gaming titles benefit from more on board Ram than a typical 1GB.

1. Is CloD one of the exceptional tiltles that requires more than 1Gb even for a modest resolution and why?

2. There seems to be an industry practice of using identical chipsets but by disabling or changing a peformance parameter (i.e No of shaders, reducing clock speeds, etc) marketing a budget version. I.e a Nvidea GTX 2GB 560 is slightly cheaper than the 560ti version yet bench tests show only a 5% reduction in performance across the most demanding games which can be adressed by oc'ing. Would someone looking to upgrade on a budget be better going for the better chipset with lower RAM or the budget version with more RAM?