APSC vs Full Frame? Image quality differences?

I will write only about my own experiences, because others have given you the technical answer, which is that pretty-much anything you can do with FF, you can do with APS-C; the only technical difference between the two (assuming proportionate MP for sensor area) is really angle-of-view.

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Personally, for landscapes though, I would say my FF has an advantage. Simply because I get that wider angle-of-view for a given lens, and also because the viewfinder (mine's OVF) is bright and large. Those two things sort of psychologically work to make me make "better" thought-out landscape images with my FF than with my APS-C.

[ I have A700 and A900, CZ24-70/2.8, CZ16-35/2.8, and Minolta 80-200/2.8 as my main lenses ].

Technically both sensors in my cameras are the same generation, so same signal-to-noise and dynamic-range, but I just find I get more "wow" pictures off the A900 because of how I use it for landscapes vs how I use the A700 (which is used more for picking off detail things with the 80-200).

So, I would say it's not the sensor-size as such, but more intangible things start to come into play, like somehow FF and wide-angle just makes me use my tripod more, makes me think and frame-up more accurately. Also for me with A900, I have grid-focussing screen, so again that just makes me set-up to take better pictures with that camera. The A900 body is bigger, and again, that just makes me think to use it more deliberately.

Sure, I can make great-great images with A700, but somehow the psychology of a bigger more-pro-feel FF camera like A900 just makes me put a little bit more time into what I shoot with the A900.

So - there's not image quality differences because of APS-C vs FF sensor-size per-se, there's perhaps usage/location/scene differences you may find when you have the choice of an FF body with a wide-angle mounted on it.

[ Obviously, others responding here are getting fantastic things from APS-C, and of course you can, and everythng I say I do with FF can be done with APS-C, but I just wanted to share my own experience based on how I find it with the two previous generation Sony models used side-by-side. I also do a lot of PP, and know how absolutely critical that is to make landscape images - of the kind you link to - really "work". ].

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Mark W.