About the NVIDA control panel settings

about the NVIDA control panel settings
theere is one of the most important settings:
choose between :
efficacy (less AA and more FPS) = and = quality (higher AA and lower FPS )

which one should i choose
(my card is gta 480 2way)

and the choose will change the game settings ???
or will only change some games settings
I really experience that it alter the 3D quality in some game but lower FPS obviously note
such as FEAR2 allmax 4AA 16AF in 1920x1200 ...
Under the same settings :
efficacy ==> 195~205FPS
quality ==> 165~175 FPS (really better quality )

Should i Set it to just depend on the game or program and not choose by myself about the
efficacy (less AA and more FPS) = and = quality (higher AA and lower FPS )
???
thx...