To sum up, we have to conclude the following:

Nvidia GeForce 7950 GX2 is faster than the Radeon X1950 XTX in the majority of cases;

ATI Radeon X1950 XTX costs $449, whereas the GeForce 7950 GX2 is priced at $599 - $649;
ATI Radeon X1950 XTX produces higher image quality under our settings due to high-quality anisotropic filtering;

Nvidia GeForce 7950 GX2 could produce higher quality antialiasing modes than the Radeon X1950 XTX, but they are hardly useful for modern games;

ATI Radeon X1950 XTX theoretically can enable FSAA with FP16 HDR, which is an advantage, however, it does not have the feature supported flawlessly at the moment and it may not provide sufficient performance;

ATI Radeon X1950 XTX, unlike the GeForce 7950 GX2, works with every mainboard provided that the power supply is capable of feeding the board with 120W of power.