Benchmarks: Fallout 3, Left 4 Dead
The Radeon HD 4870 X2 gets the edge over the GeForce GTX 295 at 2560x1600 due to the larger memory buffer, but just by a very small margin.
We can make the same observation when comparing a single GeForce GTX 260 to the Radeon HD 4870. The larger memory capacity of the Radeon HD 4870 1GB gave it the edge at 2560x1600 in Fallout 3.
Left 4 Dead is another new game and this one appears to favor the Nvidia-based graphics cards. At 2560x1600 the GeForce GTX 295 managed to render 98fps, making it 31% faster than the Radeon HD 4870 X2. Furthermore, the GeForce GTX 295 was an incredible 69% faster than the GeForce GTX 280.