Your looking at 4GB vs 3GB, and asking which is better, now if you want to ask more specifically as to what you are doing with it, that might change things, i.e. multiple monitors (3 or more), gaming, video rendering, CAD, resolution, etc, but the basic premise of which GPU itself is stronger, which runs cooler, which OCs better, doesn't change...there's a lot more to a GPU than the DRAM