Nikon D5 better known as the king of lowlight has been tested by DXOMark, recently. Whether in case of sensor or AF or burst rate and build durability, the D5 impressed much more and scored better grades.
Conclusion from DxOMark :
Moving from a 16-Mpix to a 20.8-Mpix sensor is quite significant for professionals, and the improvements in high ISO DR are useful in a camera like this. In terms of sensor resolution, the Nikon D5 now matches the admittedly aging Canon EOS 1Ds Mk II, a camera still widely used for magazine features (think double-page spreads) as well as commercial photography. While it’s true that models such as the Nikon D810 (and the Canon EOS 5DS and SR) are arguably more suited now for that kind of work, the Nikon D5 nonetheless represents a tipping point in all-around capability. With its excellent sensor performance, phenomenal AF system, impressive burst rate and durable build, the Nikon D5 is clearly optimized to appeal to those targeted by the company’s marketing department, yet its capabilities should also entice other kinds of photographers, whether they own a Nikon D810 or not.