I am no expert, but reading the reviews (and regurgitating them) I see the DDR cards only have the 64 bit buss and the SDR cards have the 128 bit buss (this is limited by the chipset). This makes the theoretical bandwidth the same, but the DDR RAM is less efficient than SDR. This makes SDR more attractive than DDR. Since the bottleneck in these cards (Geforce2 MX) is the memory you want to get the one with the fastest memory. The Guillemont Herculese 3D Prophet II MX has 5.5ns Hyundi (sp?) and does a little better in Quake III than the others with slower memory. This is the card I am buying with my Amazon/MCI promotional gift certificate. It costs $142 at Amazon vs $115 elsewhere, but free is free! Tweak3d.net reviews 3 MX boards, and Tom has some reviews too. Glue on some memory heatsinks, and this card (may) overclock better too.
Edit: If twinview is your thing, this card doesn't have it. I think they will have a future card with this option. Not important for me.
Eek!<P ID="edit"><FONT SIZE=-1><EM>Edited by Eek_TheCat on 12/05/00 05:13 PM.</EM></FONT></P>