I have a D4 and a D800. Much of my work is done in very low light settings (in dark clubs, at night, etc).
There are times where I might favor either of these cameras in low light. But the D4/D4s/Df are the cameras that can handle these situations with no questions asked.
The Sony sensor cameras, to varying degrees, exhibit color pollution (bluish-magenta with local hot spots), some think due to thermal noise caused by the huge amount of active electronics on the sensor. You can mitigate these effects with a dark frame subtraction. But this is quite a bit of extra work to do by hand when processing a large number of images. The newer cameras (e.g., the D750) have improved in this regard, but the issues have not been entirely eliminated.
There is one nice thing about the 36MP Sony sensor in low light. For the parts of a low-light scene that have better lighting, the level of detail retained is extraordinary. A relatively well lighted portrait subject in a very murky environment can exhibit lovely detail in the eyes, for example, enough to make the subject really pop.
But the D4/D4s/Df sensor is much more obliging overall. The color response is exceptionally good, and there is no need for exceptional effort in post production.
If you need to go Sony, the A7s will oblige. It uses a different sensor architecture than other Sony sensors, and is optimized for controlled noise in very low light. But it is only 12MP.
I see that Sony does not provide a lossless raw format, and some have noted that this makes their work in post much more difficult. I can't say from experience, but I am still inclined to stick with the Nikon cameras until Sony comes up with something improved. And we'll see, as the A7riII appears to be coming shortly. I'll be interested to see if Sony has finally delivered on the lossless raw format.