With the release of the Radeon HD 4870 1GB ATI is addressing a change in the marketplace created by the recent launch of the GeForce GTX 260 with 216 unified shaders. The Nvidia card was able to outperform the existing 512mb 4870 by a significant margin which the 1GB version closes and on occasion overturns.
The question of which card is better really comes down to the individual and the tasks they will be performing. In our test ATI had the edge when gaming at higher resolutions with anti-aliasing enabled, additionally the video related functionality such as Blu-Ray acceleration and HDMI solution is far better on the Radeon. The GTX however runs cooler and is more flexible for other desktop and gaming tasks such as video encoding and PhysX calculations. Read more @ DriverHeaven.