If you use CS4 versions of Adobe software, you will see gains no matter which brand (nVidia or ATI) you choose. It all depends on the specs of the card, and its OpenGL performance.
Of course, the workstation card is better for doing 3D models which require heavy vertex and pixel computations that normal mainstream or "gaming" cards have less power to do. I'm not sure if AE and Premiere benefit from using a workstation card. There must be others here who know better.