Well, looking at that womans portrait I felt quite disappointed about 6D combined with an L-lense. With my 7d and 15-85IS USM I get sharper images! 6D can do it better, as it is shown in portrait of that little girl on canons sample site. And still even this one is far from glorius! I think it was taken by a click and shoot tourist walking by...
If not, shame on canon!
Anyway, I spent 2 minutes of my time and ran a little high-pass sharpening combined with rising contrast on that failed womans portrait. Ways better, as you can see below in the first row! (After that I got a little snotty and did the same to the nikon-image - just the other way around. * g * Perhaps those canon samples got a little sabotage?! Ehm...)
Well, Nikon MIGHT do a better job here. But couldn't it be possible that the Nikon-sample got a little postprocessing as well? Combined with a good out-of-cam picture it would not be a surprise that this beats the canon-crap-sample.
After all, those are not exact the same photographies. Different angle, different light and so on. For a fair comparison you NEED the same circumstances and published raws here. This is not given, so push those sample into the dustbin.