In other words, just because the GeForce4 has more of a performance hit than the Radeon 9700 with anisotropic enabled doesn't mean that you can't have an anisotropic implementation that is invariant upon rotation about the z-axis with a performance hit similar to the Radeon 9700's.
Which also implies : it doesn't mean you can't have an anisotropic implementation that maintains the 9700 performance hit that is invariant upon rotation about the z-axis.
The point is, you speak about "fundamentals" such that nVidia isn't "fundamentally" slower. Yet using your logic, I can turn it around and say that ATI isn't "fundamentally non-uniform in quality."
In other words...I think your point concerning "fundamentals" is, well, pointless.