a lot of times OEM product are not as high quality as the retail version
Most OEM products are shipped to major pc builders they may alter it due to what the pc builder requests and it may not be exactly up to the standard that ATI wants to offer to the public plus if you buy OEM you lose the manufacture warrantee so if something goes wrong with it you cannot contact ATI but the people who sold it to you (in the early days) I bought an OEM sound blaster sound card thinking i was saving some major $$$ till after i bought it and found out it was not near the quality of the retail version.
So buyer be ware you get what you pay for!!!!
Thats not true at all. Hell, Id think OEM might even be higher quality or else the OEM builders wouldnt buy from them (honestly, if you were Dell, and you had bought a product that kept failing and you had to replace, are you as likely to keep buying from them? No).
But in any case, they are pretty much the same as far as the card. You just dont get a fancy box and the games (but you usually do get a driver CD and cables).
White/brown Box usually does not have anything but the card (no CD, no cables, etc)