From what I have been hearing from a 'Timon' on Nikon rumours, and I believe is correct, Canon cameras have electronic first current shutters and Nikons do not. So does NEX have this feature. Of course the Nikon 1 series support a fully electronic shutter which renders it completely silent, and I have coincidentally used it to excellent effect while attending a niece's wedding! I love the completely silent capability of the 1 series, of course that does not solve your problem as a pro shooter.
So just like the physical aperture linkage on non-E Nikon lenses (and every Nikon DSLR), there is a physical design limitation in Nikon cameras to do with having a mechanical first curtain shutter that constrains what Nikon can do in Quiet mode as compared to what Canon can do.
And no, in case anyone was wondering, there will be no firmware update for the D600 to enable Aperture setting without leaving and re-entering LiveView. This is another physical limitation that pro Nikon cameras work around by having extra physical hardware to support just this purpose that the lesser cameras do not and which instead rely on mirror-flipping to kick over the aperture lever.
It is very interesting, this meld of physical engineering and electronics and firmware that is the Nikon camera