Jesus, AGAIN.
Name one person who would switch on MSAA 4x to go from 80fps to 35fps? The answer is none, so again you've highlighted yet another card that ISN'T effected by memory in ANY SITUATION YOU WOULD ACTUALLY USE IT.
Top to bottom the only setup I would use 4xmsaa with would be the 570 sli, because its the ONLY setup that has enough performance out of those for a really good experience at that resolution........ and it isn't memory limited.
I wouldn't even run a single 580gtx with 4xmsaa from those results, it too has enough memory.
FXAA won't kill the 560gtx performance to unplayable levels, nor will it max out ram usage, this is why 0% of 560gtx would even think of using 4xmsaa, and the 1gb memory will not effect them when they don't.
You lose, AGAIN. As per always, you are NOT the first person, or the 100,000th person to know that higher settings uses more memory and there are situations more memory will help. The problem is your crusade is 1920x1080, and you have failed, again, to find a situation where a 1gb card is memory limited. You found a situation where performance is low on a 2gb, a 1.25 and a 1.5GB card that you WOULD NOT USE THOSE SETTINGS, so the fact that the 1gb card also suffers at those settings, is irrelevant.
Again and again you fail to find situations where using a 2gb version of a card gives playable experience but 1gb doesn't..... the 2gb 560gtx would ALSO give too low performance here.