1/ Read noise:

First good surprise: the 6D is better than the 1DX and 5D mark III (it is close to the 5D mark II) at low iso. At high iso, it is almost identical to the 1DX, with only 1.7 electron at 6400 iso.

2/ Dynamic range:

Second good surprise: the 1DX remains the best, in particular because of a higher photosite capacity (81600 electrons vs 70000 for the 6D), but the 6D holds out on the 5D mark III and mark II, especially at high iso thanks to its lower read noise. At low iso, it is the winner of the group by a short head.

3/ Banding:

Banding is still present, but here too the 6D is in the head of the group, especially at low iso.

Conclusion : Canon kept its usual sensor technology with its well-known limitations compared to the Sony sensors (lower dynamic range at low iso, banding not totally cancelled), but it succeeded in obtaining sensor performance almost similar to those of the 1DX and noticeably superior to those of the 5D mark III. On the sensor point of view, the 6D clearly offers the best quality/price ratio of the group.

Note: these results come from one particular camera. Another one could give slightly different figures.

Thanks to Rémy Courseaux for his 6D files.