They all use the same chipset, which 90% of the home market comprises either ATI/AMD or nVidia. There is a basic reference design that the manufacture's must follow closely in accordance with ATI and nVidias license/specifications to manufacture. But some parts as mentioned above, like cooling, BIOS tweaks, memory, etc set brands apart from each other in some way. In time, people have made decisions based on the experience of others or their own personal experiences. Some people form valid points that can be applied directly, "the fan on that Duramax GTX 295 is really loud" or "the card would not work when I bought it, and it took me 3 weeks to get someone to answer the phone at customer service" Warranties and customer service are important to some people, to others (like me) we could care less.
For every person who has good things to say about a certain manufacturer, there is going to be someone who has had an equally bad experience with them. I buy from retail stores. It is a little more expensive, but I find that if there is a problem, it is going to be right out of the box. And if it don't work, I go straight back to the store and get one that does. I don't argue, haggle and wait for a week, or two, or three, 5 phone calls and 15 emails. I have better things to do with my time than deal with nonsense and returns via UPS, Fedex, or snail mail.
I also would never buy anything made by EVGA.
