ATI, until the Geforce 8800's came out, only 2 advantages that they could market:
1) Image Quality
2) AA w/ HDR
Now both of those are gone. And besides, you're trying to compare a prototype X1900 Mobility card to the performance of a downclocked Dell Nvidia card. ATI cards can't be flashed for crap... I'll stick with Nvidia as long as they are still around.
I used to like ATI for long time, because the text quality is way better than Nvidia (that was 4 years back). And now Nvidia has improve the text quality so as the image quality, it is better choice than ATI. Especially in mobile version GPU, Nivida is way in the lead compare with ATI. In gaming world, ppl usually pick Nivida as their first choice. We all want a fast GUP and Nivida is the answer.