I bought a couple of 5850s from a UK videocard webshop recommended on this forum - cheap for new cards - but no obvious brand, I guess the cards were 'whatever they could source'. When they arrived, the cards turned out to be XFX 'Black Edition' 5850s.
Given the hyperbolic horseshit on the packaging, I was expecting the cards to be good overclockers, at least up to the level of my 'old' 5-heatpipe Sapphire and the two Sapphire 'Extreme's that I use. However, the XFX base clock was 735 MHz and they were a bastard to clock up to respectable rates.
My 'old' Sapphire card does 406 MH/sec with a 990 MHz core clock. The 'extreme' cards can only push between 370 and 390.
The XFX 'Black Edition' examples I have (only two, so not statistically significant) only clocked to 360 MH/s and that took ages to reach, with a finely tuned memory clock. The highest core clock my cards could manage was 930 MHz - the other one couldn't better 900 MHz. Perhaps the Sapphire cards run at higher voltages and can clock higher? I don't know - but all the bullshit about the 'Black Edition' being some top-bin part, capable of heavy overclocks, seems to truly be bullshit.
That said, I don't over-volt cards. Perhaps the 'Black Edition' *is* a strong top-bin chip and can take big voltage increases, and with the voltage increase the chip can be clocked a lot higher. It's not just a principle thing about not wanting to strain the VRMs and reduce the lifespan of the board - I'm running Linux on all my miners, and voltage tweaks under Linux aren't easy (either that, or I don't have or know about the tool).
Has anyone here with XFX 'Black Edition' cards found them to be 'super' GPUs? Or is the marketing the steaming pile of dung it appears on first impressions? Still, overall, the old retail Sapphire 5850 from PC World - not 'extreme', not 'limited edition', no bullshit - is my fastest card bar none. I've been getting over 405 MH/s for a month now 24/7 on the standard voltage... just 990 MHz core clock, 300 MHz memory (was using 275 MHz memory, but this gave 403 MH/s)...
From my non-significant sample, I'd go with Sapphire cards every time.