part of it may be that non-vivo cards are like 10,000 % more popular than vivo. so you see lots more people overclocking non-vivo's and getting awesome results and such. also, in the case of the radeon 8500 dv they put ****ty ram on the card and made it worse than the normal 8500, so that might be part of the myth too. but like cisco said, as long as its the same ram and all it should be the same overclocking ability as well.