Nvidia wants to stick with a two to one ratio and assumes that the games of tomorrow will need twice as many pixels than they will need vertices and geometry information.
ATI believes in a different religion. ATI believes that every Shader should become one, united and bellowed. No more segregation to Pixel and Vertex Shaders. If ATI makes a chip with 64 Shader units all of them can do Shader either vertex or pixel or geometry stuff all the time. You can check the stories at the bottom for a better explanation.
We don't know the clock speed of the upcoming performer but we don't believe Nvidia can get more than 700MHz out of it - we could be wrong about that. µ
See Also
Nvidia G80 meets DX 10 spec with
'dis-unified' shader
Nvidia G80 is taped out