All the reviews show the ATI beating the GF2 in 32-bit color, but not in 16-bit color. Why? The GF2 has more rendering pipelines, but the ATI is more efficient with memory bandwidth because of better Z-buffer management.
Oddly, most reviews seem to conclude the ATI is a bit slower overall, since the 16-bit color scores are lower. The FiringSquad ran more tests in 16-bits than in 32, then actually said the GF2 was faster "in a majority of our tests". Anand does an OK job, but he still has graphs with 16 and 32-bit color grouped together, with the sort order on the 16-bit color results.
So the ATI wins in every important performance test (i.e., who gives a rip about 16-bits?), but the GF2 comes out looking faster. Reader beware.