The 6D is much more capable when it comes to dynamic range than the Crop canons I have used.
The croppers are better than they're being given credit for.
This is a random 160 ISO 70D CR2 I picked up off the web somewhere.
And this is how it looks (white balance not addressed) with the shadows slider pushed to 100 and a stop of +ve EC added in Capture One - about 5 stops in total on the shadows. Default NR, no other changes made.
Looks OK, doesn't it? All the detail that was hidden in shadow is there.
Here is a 100% before crop; and here's after.
Nothing much wrong with this. Yes, there's a little bit of "texture" where the shadows were darkest; but the detail is all there and there's no pattern noise.
Pointedly, it's not at all far from what the "magic" Sony sensors are capable of...
The thing your missing is that detail buried in "shadow" isn't the problem. It's detail buried in READ NOISE that's the problem. "Shadows" extend for hundreds to thousands of levels...read noise usually only intrudes a dozen or so levels into the deepest of shadows. It's those very deep shadows that mark the difference between a Canon sensor and an Exmor.
The image you edited is more along the lines of this:
Being lifted to this with a +3 stop pull:
The "shadows" are not totally buried in the read noise...so they are nearly fully "recoverable". Which is a very far cry from this:
Being lifted to this with a +5 stop pull:
The detail here is not just "in shadow"...the detail is completely buried well into the noise floor on my 5D III sensor. It's near impossible to recover...it's riddled with red banding, and the noise level in the deeper shadows is two or three times what it is anywhere photon shot noise limited, as it'c compounded with dark current and various forms of noise caused by readout. It's these extra two stops...which, when you get right down to it, don't actually represent a ton of tonal levels...maybe 10-30 at most, if that...it's these deep shadow levels where the read noise exists that mark the difference between a Canon sensor and an Exmor.
The inevitable question that comes after I try to make this clarification (either when defending Canon, or when defending Exmor...these days it doesn't seem to matter), is: Why would you ever need those extra two stops? or How often do you actually have detail buried that deeply?
Sure, this isn't an every-day case. Some types of photography NEVER encounter a situation like this because they are always shot at higher ISO where DR is limited by physics. That said...even if the situation is a niche situation, it doesn't change the facts. The facts are...Canon sensors currently suffer about a two stop disadvantage or handicap compared to Exmor, and a one to two stop disadvantage compared to many other sensors on the market, such as the Toshiba sensors used in Nikon's D5000 line.
The next statement that is usually made is, the detail buried way down near the read noise floor in a Nikon RAW file can't possibly be clean, low noise, high color fidelity detail. Here are two images I downloaded way back around the time the D800 was released (shortly after the 5D III was released...about the time Fred Miranda wrote his review of both...I was looking for some real evidence to prove, either way, whether Exmor had better low ISO DR):
These two images, which are large (click on them for full size) show the exceptional quality of detail you can recover out of deep, black shadows.
The images were originally downloaded from here (although the link seems to be dead now):
The difference between current Canon sensors, and an Exmor, is not "you can lift shadows". We've been lifting shadows for years. The difference between the two is that you can lift ultra deep shadows that would otherwise be buried in red-banded read noise on a Canon, by 5-6 stops on an Exmor...and STILL have decent color fidelity and clean, random noise.
If you need that kind of shadow recovery capability...and I stress IF, I still believe a majority of photographers tend to shoot some kind of action at higher ISO, in which case Canon sensors have a very small edge over Exmor sensors at higher ISO...then don't hold yourself back. Canon may release something that can do what a D800 could do over two years ago at some point...but why wait until that unknown future time, when you could solve your problem now with a Nikon, Sony, or Pentax (or any number of other cameras that use Exmor sensors)?
This is absolutely impressive...