I know this topic is long dead, but somehow I was searching more comparisons at night shooting scenario between 6d vs 5dm3 and came across that topic (also in this forums here). I think that below article comparing 6d to 5dm3 (and later also to 5dm2) at iso 3200 & 6400 with 15 sec & 30 sec exposur
An overall DxOMark score of 82 put the EOS 6D right at the top of the tree in terms of Canon cameras, matching the score produced by the flagship EOS-1D X. In the sensor rankings, it ties with the Nikon D3s and the medium format Pentax 645D. However, this does only rank it around 10 th, a fair way below the current top rated camera, the Nikon
supports Wi-Fi 5 (802.11ac) Canon EOS 5D Mark III. Panasonic Lumix S5. 802.11ac wireless works on the 5GHz frequency range. It offers higher transfer rates, improved reliability, and improved power consumption. It provides advantages for gaming and HD video streaming.

The 6D would be an upgrade from the 5D, even compared to the 5D MK II. In low light noise the 6D even has an edge over the 5D MK III, but it is really splitting hairs, but the 6D features are less than the 5D MK III and the 6D with only one SD memory card slot and requires using the menu system to change white balance, so not as easy with buttons to quickly access some features.

The 20MP Canon EOS 6D is Canon's smallest, lightest and most affordable full-frame DSLR yet, aimed at enthusiast photographers. As well as a newly developed CMOS sensor the 6D features an 11-point autofocus system with a single cross-type point at the center of the array, which can achieve focus down to -3EV, which is little more than moonlight.

. 234 141 427 305 224 135 113 393

canon 5d mk3 vs 6d