7800GS Is The Clear Winner
The GeForce 7800GS is a solid card for anyone looking for Shader Model 3.0 support on the AGP platform. It clearly is head and shoulders above the GeForce 6800 Ultra, which also provides SM 3.0 functionality. Going head to head against the ATI Radeon X800XT and X850XT Platinum Edition, it is the AGP king.
As for the crown on the 7800GS king, the EVGA "Superclocked" version has the extra clock cycles to put it ahead of the BFG "Overclocked" version. There is rumor of another version clocked even higher than the "Superclocked" version from the guys at EVGA. From what we can tell, we wouldn't be surprised to see additional cards with higher clock speeds from other vendors as well.
We feel that either card would make a viable upgrade path for your existing AGP configuration, but we also continue to stress that it makes sense to make the leap to PCI Express whenever possible, as that is where the rest of the graphics market is moving. If you are on the verge of making the switch, keep saving your pennies and upgrade your entire system. If cost is too much of an issue, or you just have to have the "latest" graphics card technology, the GeForce 7800 will serve you well for current and future SM 3.0 titles, at least for another 9 to 12 months.