This was fine until you mentioned the 5D3 not being much better than the 6D for f/1.4 portraits using the outer AF points. The 5D3 makes the 6D look broken doing this and it's a shame a 60D or a 7D would also make the 6D look broken.
- The 6D's -3 EV lowlight sensitivity is currently unmatched by any DSLR on the market
If you shoot lowlight, sunsets, night photography or landscape photography the lowlight AF performance on the 6D wins.
As I pointed out a few pages ago in this thread:
How do you define 'low light'? For example, the difference between shooting at -2 EV and-3 EV could mean 1/15 s, f/2.8, ISO 51200 vs. 102400. Neither is very usable from an IQ standpoint. What most people call 'low light' is generally substantially brighter than either spec.
Long exposure night photograpy might benefit from that extra stop of AF capability (but in that situation, you are on a triod and probably using Live View to focus anyway). Sunsets, landscapes and general shooting have plenty of light relative to the AF sensitivity of even lower end dSLRs.
I think the -3 EV spec of the 6D is Canon saying 'we did it because we can, and to throw a bone after otherwise limiting AF functionality of this body' - it looks good on paper, but is of little practical benefit in the vast majority of shooting situations.
As I've said many times, due to the low noise of the 6D, the low light sensitivity of the center AF point, can be very useful in the majority of situations where you are shooting wildlife (or people) around, before, or after sunset. Or else if you are shooting landscape hand-held, with an IS lens, up to an hour after sunset...or during a full moon. Or if you are shooting inside a club, or outside on a dimly lit city street at night, that -3EV capability is very useful.
ISO 6400 is extremely usable for professional prints via the 6D (with a bit of post processing), and ISO's a bit above that are still useful.
As for bashing the other AF points on the 6D, you need to bash the 5D2's as well, because they were no better. It might not still be on sale, but plenty of forum readers still own and use the 5D2.
For anyone shooting with strobes, or shooting fast sports action in well lit areas, the 5D3 or 1DX is the camera you need (or perhaps a D800 at low ISO).
If you're shooting portraits with an f/1.4 lens, wide open at f/1.4, and require peripheral AF points to be used (for focusing on eyes, etc.), then yes the 6D will not give consistent results. But then the 1DX and 5D3 don't fare much better in that situation, which is why serious portrait photogs who shoot this way, either manually focus, or use live view. Of course most of them are closing that fast lens down quite a bit, in which case there is more wiggle room for AF inaccuracies.
And besides, in that peripheral area of these lenses (other than the Zeiss Otus)...those eyes that you claim are so razor sharp...actually are not, and are suffering from coma and astigmatism. It's unavoidable...especially with such lenses as the 50L and 85L.
+1 with RLPhoto, I have no problem with outer AF points on my 5D III. Doesn't matter 85L II or 50L
Photo below was taken with 5D III + 50L, outer AF point @ f1.2. Oops...sorry, that was f1.2 not f1.4 as he mentioned
That's a chair, not someone's eyes. Post one of those please.
A lot of thing to say...little to show
1st photo SOOC, untouch: 5D III + 85L II, 1/160 @ f1.2, outer AF point, was focus on her left eye
2nd little edit in LR
BTW, I have no problem using AF in -3EV lighting condition, yes, with 5D III. Wanna see sample photos?