http://www.dxomark.com/Reviews/Canon-EOS-1D-X-Mark-II-sensor-review-New-class-leader
"The Canon performs exceptionally well. Not only does it have a wider useful dynamic range at base and low ISOs than the Nikon, it’s not far behind the Sony, and that small difference won’t be noticed in use. The Canon sensor continues to offer a wide dynamic range at every ISO setting, improving on the Sony from ISO800 onwards, and falling only slightly behind the Nikon’s strong performance from ISO6400 onwards. Indeed, the difference at most is around +0.6EV. Canon cameras are known for high ISO noise performance, and the Mark II surpasses both the Nikon and Sony by nearly +0.5EV.
Conclusion
This is a well-deserved result for Canon, and this versatile sensor should prove attractive to a wide range of photographers, including those that work in multiple disciplines. The wide dynamic range at low ISOs should appeal to all photographers, but especially those using it for landscapes, and the low noise at high ISOs will also appeal to action and sports photographers. Although the new model is aimed primarily at that market, the increase in pixel count over its predecessor now matches that of the earlier EOS-1Ds Mk III, a model that’s still highly regarded for editorial and commercial work. It is not too much of a stretch to view the new EOS-1D X Mk II as the natural successor to that camera, and its wide range of capabilities, including DCI 4K video, make it look highly tempting. Sure, it would have been great to see a higher pixel count, but overall, the sensor performance offers photographers the versatility to tackle a wide range of assignments with just one camera."
"The Canon performs exceptionally well. Not only does it have a wider useful dynamic range at base and low ISOs than the Nikon, it’s not far behind the Sony, and that small difference won’t be noticed in use. The Canon sensor continues to offer a wide dynamic range at every ISO setting, improving on the Sony from ISO800 onwards, and falling only slightly behind the Nikon’s strong performance from ISO6400 onwards. Indeed, the difference at most is around +0.6EV. Canon cameras are known for high ISO noise performance, and the Mark II surpasses both the Nikon and Sony by nearly +0.5EV.
Conclusion
This is a well-deserved result for Canon, and this versatile sensor should prove attractive to a wide range of photographers, including those that work in multiple disciplines. The wide dynamic range at low ISOs should appeal to all photographers, but especially those using it for landscapes, and the low noise at high ISOs will also appeal to action and sports photographers. Although the new model is aimed primarily at that market, the increase in pixel count over its predecessor now matches that of the earlier EOS-1Ds Mk III, a model that’s still highly regarded for editorial and commercial work. It is not too much of a stretch to view the new EOS-1D X Mk II as the natural successor to that camera, and its wide range of capabilities, including DCI 4K video, make it look highly tempting. Sure, it would have been great to see a higher pixel count, but overall, the sensor performance offers photographers the versatility to tackle a wide range of assignments with just one camera."