I think the Sapphire which is the biggest partner of Ati makes the best cards. After my x850 xt pe and x1800 xt i can say that easily. The cards are decent overclockers without any problems. I do advice Sapphire.
I think that these days, the enforcement from ATi to the companies making ATi cards, is so strict that any make is good. Ati wouldn't let someone represent their VPU's with lacklustre components. So for sum1 just looking for card xxxx, any make should suffice.
Where different brands start playing a role is with innovative designs - for example HIS and their excellent cooling options, and lately ASUS with their innovative cooling option.
Some people value a package with all types of goodies in it, that might also be a desiding factor. So it depends on what the company offers the consumer.
Personally, I prefer less goodies, more after sales service, good warrantee circumstances and if possible a cooling option that works well.
Currently I have a Gecube 1900 series card. My first Gecube, and I like it! They gave me a manual that was completely english, and a rough guess 40 pages long - describing almost everthing one would like to know of one's purchase. But I'm still open to other companies!