Hmm. LensRentals did a controlled test and the results don't support your enthusiasm.
In terms of AF accuracy, the 6D is closer to the 5DII than the 1DX/5DIII.
I don't think Roger Cicala was being consistent in the above article.
If we list the AF standard deviations of previous Canon cameras tested by Roger using the new 28 f/2.8 IS USM, this is what we get:
5D II 38.5
5D III 17
If we group them according to AF consistency of the center point, this is the result:
Tier 1: 1DX, 5D3... 1D4 trailing slightly
Tier 2: 6D, 1Ds3, T4i... 50D, 60D trailing slightly
Tier 3: 5D2, 7D, T3i
So, yes, the 6D beats out the 5D2 (and the 7D too... consistent with my experience).
I think it's the same as Roger Cicala's comment later in the thread.
On December 1, 2012 at 6:55 AM
Roger Cicala said:
Ralph, I guess I was writing from the ‘is the 6D as good as the 5D III. The standard deviation the 5DIII and 1Dx were in the teens, which is exactly where live view or careful manual focusing is.
The 6D at 29 is actually almost exactly the same as the T4i, so it’s not as good as Live View. But it is better than the 5D II and other older cameras.
And, of course, with most of the lenses in the lineup the difference doesn’t show up, only the newer lenses are capable of the more accurate AF.