...show me a 6970 pulling 445MH/s at 1ghz core like the 5870 does.
Here:

I have it at only 950core/1375Memory doing an average of 460+MH/s (values fluctuate between 457.8, 460.5, 468.7). Still, a 5870 is far more efficient at mining since the GPU is smaller by half a billion transistors, it has half the ram clocked at a lower speed and at lower voltage plus the PCB is less complex (less layers).