After some testing the problem is rather SGSS than AA on my system, even with GTX680.

Heavy clouds are still a killer with SGSS enabled, with 8xS instead of 8x SQ and 2xSGSS there's nearly any difference here.

 

I can see how SGSS would overshadow regular AA performance wise, and even though 8xSQ is a fair bit more demanding than 8xS, once SGSS comes into play that's what going to determine performance in clouds. Nonetheless, I wasn't talking about performance but about visuals. With 8xS you get 4 multisample runs vs 2 of 8xSQ. On the other hand 8xSQ has better supersampling, but with SGSS you have that covered. That's why I think 8xS is probably a better fit for SGSS, but must admit the difference in IQ is nothing to call home about

I can see how SGSS would overshadow regular AA performance wise, and even though 8xSQ is a fair bit more demanding than 8xS, once SGSS comes into play that's what going to determine performance in clouds. Nonetheless, I wasn't talking about performance but about visuals. With 8xS you get 4 multisample runs vs 2 of 8xSQ. On the other hand 8xSQ has better supersampling, but with SGSS you have that covered. That's why I think 8xS is probably a better fit for SGSS, but must admit the difference in IQ is nothing to call home about

I can see a small difference only in outside view on the aircraft, therefore I've 8xSQ activated, but perhaps this is up to my monitor because of a dot pitch of 0.30.

With a smaller dot pich one may see no difference between these modes. I will test IQ with a 24'' TFT instead of the 27''.