How does the Xpro compare vs D600 / D800 / MKIII on High ISO?

Hm.  Care to elaborate?  Every review I've seen states otherwise.

They say that it has about the best S/N ratio among all current APS-C sensors, and that while it uses noise reduction, the removal of the low-pass filter allows the noise reduction to be more aggressive without destroying as much details as others, the result is the retention of more details than any other APS-C cameras.

i.e. not just "isn't that different than applying noise reduction", and definitely not "retains the least detail".

If you have evidence supporting your claim in contrary to most if not all existing reviews, feel free to share.