Geforce 6600 GT vs ATI XT1300 AGP

6600GT would be my preference.

I agree. I bought two PNY 6600 AGP cards for two of our Intel mb P4 2.66 HT
systems and they have performed great. I had to RMA one because it locked
up during highres game play, but PNY replaced it quick with a complete new
retail unit. I purchased a PCIe X1300 for my new P965 E6300, but the
performance was disappointing. I upgraded to the 7600GS and it simply
ran rings around the X1300 and it was only $20 more at the time. I've been
an nVidia user for a long time, only straying from the fold when I bought a
9600SE for my son because he likes Halflife. Since I've given him the 6600,
he's content. For now... .

I agree with the above poster. Go look at the vga charts. However, keep in mind that that new 1300XT is what used to be a 1600pro. It had a rename and a price change is all. The 1300XT (1600pro) does perform a little better than the 6600gt in SOME games, and worse in others. Looking at the charts for 6600gt vs 1600pro will give you a good idea as to what you are comparing.

Good luck.