I believe it depends whether you want to keep the card for a long time or not. Personally I would choose the GeForce DDR and save the $50. NV20 and other fully DirectX8 accelerators are just around the corner, and IMO this is one of the worst times ever to buy a fast gaming video card.
DirectX8 together with Xbox will make a dramatic difference in feature utilization of new games. By the end of this year (if everything goes according to M$'s plan), there will be several high-profile high-budget Xbox games out there, which'll also have nearly identical PC conversions. In order to be able to play these games to their fullest, you'll have to buy a new video card. This doesn't only concern those with low-end cards, but also those with GeForce2 Ultras and ATi Radeon 64MB VIVOs.
This shouldn't be considered as a bad thing. First of all, it ensures several high-budget games for the PC platform which otherwise wouldn't have happened at all - Xbox games might not be 100% binary compatible (or are they?), but conversion won't be much more than a recompilation with minor tweaks. Second, it brings all gaming up to a certain technical standard. Those with not enough budget will certainly find it easier to buy a Xbox, and hardcore gamers with big-$$$ gaming rigs will finally get games which fully utilize their hardware.