5 ATI shader cores work as effectively as 1 nvidia cuda core. 5870 is about 1600/5= 320 with 850mhz core speed and while ram wont matter in FPS anymore, cauz no one rly plays above 1920x1200. So nvidias incoming GTX480 has 480 cuda cores clocked at 700 mhz.
Basically Nvidia more cores with lower speed and ATI less cores, but higher clocks, the real difference can be told from benchies.
Basically Nvidia more cores with lower speed and ATI less cores, but higher clocks,
What are you talking about? nVidia's clocks are much higher GTX280's shaders are 1.3Ghz, and the GTX480s are above 1.4Ghz. You're confusing core speed with shader speed, the core speed affects other things like the TMUs and RBEs.
Then you forget that the old nV shaders are dual issue (double pumped) SPUs.
Seriously it all comes down to the math they can do, and the math required for an operation, and that's just the shader part, not even talking about texture and other components (RBE, Cache size and layout) that govern speed.
Check launch reviews of the architectures by places like Beyond3D to get more detail on exactly how they work and how it's not just about the speed.