I think for the basic guy buying a card, the XT vs XTX principal applies where XTX is overpriced. IF, one is to OC, then the argument might move a bit to the XTX. Still expensive in my view
Some people have the cash to blow on the very best, some buy from 3rd parties to save some bucks etc.. I got my first Foxcon (seeing that ATi is fabless GPU manufacturer) X1800XL (non OC'd) last year, and after 2 months it blew an IC on the backside - and there I was thinking that built by ATi was supposed to be the best compared to 3rd parties. I don't blame ATi, as component failure is the result of poor errmm, components, not engineering on ATi's behalf.
One should also keep in mind the complexity of the cards and the amount of components - and a resistor or transistor failing doesn't make the 3rd party bad, it is just bad luck.
We are also dealing with a wide scale of users, and thus the failure rate seems huge because people post to the most popular web sites their failures where all attention is concentrated, and in most cases manual intervention can counter encountered problems ie. overheating of x type gcard (but the person has a case cluttered with cables and case temp of 40+ while gaming).
My sequence of cards
Hercules 9800XT - Still working
VisionTek X800XT - Still working
Built By Ati X1800XL - Blew
XFX 6600GT - Still Working but trivial in this matter
GeCube 1900 - Still Wokring