Seriously, the noise?
From an engineering perspective, the AMD is the lower power card and is thus easier to cool. Harping on about the noise is PATHETIC.
From what I can see, the 4Gb 6990 is 5% CHEAPER as well.
Yes, there's also the powercolor water block for a LOT less than the water-cooled 590.
Both are impressive, fantastic graphics cards but seriously, the noise?
Let's for a second consider who would actually spend the money for one of these... I don't know a single soul who'd buy either. They're marketing eye candy so cut the nonsense and tell it like it is.
Where is the action? Good enough gaming. What's the best 1080p gaming card? 6770-6850 + GTX 460
I won't say anything above that is superfluous but it's not far off.
If you're spending more on a card than that, you're looking at obscene hours of gaming to recoup your "entertainment budget investment". Translation: Give to the poor and get a life rather...
I'll say it again, this is a marketing card because you're probably buying amd or nvidia because you aspire to having the ludicrous "ferarri" of all cards but know better than to buy one.
Here's me with my GT240, bought because I *can* game with it at 1080p with lowered details but it's low power for standby use (it's in 2D most of the time) and I didn't need to upgrade my PSU for it either. It gets hot here so these are reliability concerns.