The issue of banding and so on is one that comes up fairly often from serious landscape shooters, people who are often really pushing their cameras to record very wide scene dynamic ranges...people whoa re doing HDR type tone-mapping...shooting toward the sun or bright sky areas and who want to take multi-frame shots and then combine images....looking for the absolutely widest dynamic range AND the absolutely cleanest, most-pure shadows, with the least banding, and the absolute least possible chroma noise.
Notice those color speckles, the chroma noise in the three Canon-made sensor cameras? Those shadow areas from the test target SHOULD, ideally, be deep, pure, clean black areas and low tones, like say, the shadowed areas beside a log in the forest, or the shadowed side of a boulder in landscape, or the dark areas in a High-ISO sports shot...
And, not to put too fine a point on it--but please do look at that GRAY box area in all six of the above test images...notice how that is ALSO showing a lot of image quality loss in "some cameras"? We're not talking about only the black areas...this noise and banding is not confined only to the darkest tones...it's somewhat, uh, what's the word? Pervasive maybe?
...now, as long as you keep those areas DARK, and free of visible detail, the banding, the noise, or the combination of banding and noise, will be virtually, or mostly, invisible. The real advantage that Sony's latest-generation sensors have brought--when combined with Nikon's electronics and image processing pipeline--is the advantage of a much,much,much wider range of in-camera exposure options AND much wider post-processing file manipulation before the images start to reveal fundamental-level flaws.
The question is: how clean do you really want the shadowed areas to be? Do you want to be able to do a two-frame merge, or a three-frame merge, or are you happy doing a 5-frame merge, in order to get CLEAN, PURE, unpolluted, non-banded shadowed areas? Do you want to be able to do a SINGLE-frame shot with over 14 stops' worth of dynamic range with each shutter click, at Base ISO?