Its all BS. You will never be able to tell the difference.
The comparisons some people have pointed out are retarded. When ATI tells you your getting a video card with "this clock rates/memory", this amount of pipes, etc, with PS2, etc, YOUR GETTING THAT CARD. Your not getting a 3DFX card that has a red PCB with a Radeon HSF and then call it "close enough". What the card puts out, we as consumers and reviewers will determine whether its worth our money, whether or not you can actually tell performance and image quality differences. Bill Gates did not create an OS monopolistc empire by allowing the user to do whatever the F*ck they wanted to get whatever the F*ck the user wanted out of it, you play within the rules of the OS itself. Same thing applies to ATI/Nvidia cards.