And big boys say NVidia cheats on 3D benchmarks.
hehehe I think NVIDIA termed it a "Product enhancment". That is the NVIDIA Drivers detects when 3D Mark was run and drop the texture quality slightly (plus other things I guess ) to produce a slightly better result. ATI do this as well. They just don't get caught.
What you have to remember is though is that AOS4 won't have DirectX. It will use Mesa aka OpenGL. Given this, NVIDIA has always been an OpenGL Card. The drivers support directx though. ATI is designed to be a directx card. As such NVIDIA cards have an edge in OpenGL performance over ATI.
It really doesn't matter what card you use. There wont be anything on Amiga that needs such awsome power of the Radeon 9800 for a long time ( if ever ). So it will just be a bugdet prefference unless your religion prohibits you from buying NVIDIA ;-)