hello
i have a fx5600xt (nvidia) but i get lower result with glxgears :
with my ati 9500 pro : around 5000 FPS
with my fx5600xt : 1300 FPS
glxgears is not really meant for benchmarking ... better install quake III :) (half kidding) or see how much you can increase the gemwin fps with the same scene.
on the other side, i don't think that ATI cards support anti-aliasing (FSAA 1,2,4).
they do
nvidia does. and finally, i never been able to extend my windows manager to use the other monitor. i've only been able to add a second head(DISPLAY=:0.1). so no 2d or 3d acceleration (XV) on the second head for me.
ati's fglrx drivers works very well with "big desktop mode" providing gl and xv acceleration.
+! aym3ric.