We've judged the two cards each in their own right, but how do they fare when they're compared directly?
Performance-wise the GTO has the edge. It won all of the game benchmarks except for F.E.A.R. and it also came first in 3DMark 05. The 7600 GT beat it in 3DMark 06, though only in the four tests it could do out of 12, due to the fact that it won't do FSAA with high dynamic range (HDR) enabled. So if you're in to the few HDR titles that are out there, you might well want to consider the X1800 GTO in favour for the 7600 GT.
Both cards have their own video processing systems, Avivo on the ATI and PureVideo for Nvidia. Neither yet offers as stand-out benefit over the other. The 7600 GT comes on a more conveniently size board than the X1800 GTO, sports a more friendly, less intrusive cooling system and it doesn't need an extra power feed.
But with the recent price cut, the X1800 GTO has one other advantage: it's cheaper than the 7600 GT, though the difference isn't huge. For now, then, the scales tip in the ATI product's favour. For now... ®