<p>Seems to be some pretty poloarised views here.</p>
<p>I, too, have both bodies, married with the same lenses as the OP, with the 6D as my back-up.</p>
<p>Both are great. I have had no issues with dynamic range or muddied shadows in either. However, I do not have a Nikon or Sony to compare against.</p>
<p>The AF and build quality is significantly better in the MK III. The Wifi, GPS and lighter body better in the 6D.</p>
<p>I think, unless you have specialist, high end needs, you will be happy with either.</p>