It is probably the 3dmark05 focusing on newer DX9 pixel shaders holding the 5700 back. The fx5xxx series had some issues with modern tech. I am sure if the test was 3dmark2001SE, the 5700 would smoke the x300
NVidia obviously learned from their mistakes, since the 6600GT/6800GT were dominant in their price classes for quite some time before ATi fielded the X800XL at $300, which drove down the prices for every card that was $400 or less. It is funny how the tables turn, now the ATi cards are the ones behind in the pixel shader department, so the X800XL has a lower 3dMark05 score even though the stats show it should be marginally faster than a 6800GT.
Personally, I am very happy with the X800XL performance. In the games I play I am getting what I wanted: 1600x1200x32 at FSAAx4, AFx16 almost locked at 85 fps by vsync
