Despite each card's different shipping specifications, they all demonstrate similar maximum stable overclocks:
As you can see, the overclocking results fall very close across the playing field, except for the strange advantage shown by MSI’s Twin Frozr II/OC at 2560x1600. This is an odd and inexplicable result that manifested itself with repeated testing.
reason for MSI's faster performance : faster memory?
though there is a triple slot 580 from ASUS that should also be included.
with all the talk on how the 590 is the 'flagship' card or the 'meat and potatoes',
it's the 580 that really brings home the bacon..