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 The differences aren't too significant here, but the new model is actually a touch smaller and lighter than the EOS 5D Mark III. It measures 150.7 x 116.4 x 75.9mm (next to the EOS 5D Mark III's Canon EOS 6D vs. Canon EOS 5D Mark III The Canon EOS 6D and 5D Mark III are both previous-generation models that can be found at good prices on the used market. Which is a better fit for The shutter life rating on the 6D’s shutter is 100K actuations. The 5D3 is rated for 150K. If you are the kind of user who is likely to hit the higher shutter count during your use of the camera, this is definitely a consideration. That being said, replacing a shutter is around $300; it’s not the price of a new camera. As for your question, if youve got the money, the 5D IV is the way I would go. Better sensor, resolution, joy stick, dual card slots, are just a few things that make it a no brainer (for me at least). Coming from a crop sensor to the full frame sensor equivalent to the 5d IV, I am blown away by how high I can push the ISO and still retain quality. I'm astonished that Canon continues to peddle their soft mushy DLSR video, while Panasonic, Sony, and even Nikon produce vastly superior video quality. I still love my Canon equipment (1Dx and 5D-MkIII), but definitely not for video. Sorry if any Canon users are offended by this. The 6D is Canon's entry level full frame. The 5D Mk III a pro level full frame. As an entire package it is just a better camera, IMHO, of course. So I guess you know my answer, get the 5D Mk III and don't look back. You are aware that your EF-S lenses will not fit on a 5D ? Another word about your lens choices. Which are pro and cons of 6D, 5D MkIII and 7D MkII? I'd prefer to not use Magic Lantern and just go with a nice Log-C profile, maybe recording externally in ProRes if needed for bigger projects, but the codec with Andrew's profile looks great until 3200 ISO on 6D. 54Vib06.

canon 5d mk3 vs 6d