In the spare time I have made some shots with both lenses. Definitely this is neither a scientific analysis nor neutral comparison. This is because Fujinon was working on X-Pro2 – 24 Mpx, while Nikkor was on the D810 – 36 Mpx. Why this way? The simple answer: I don’t have any APS-C Nikon body. A bit more complex answer: Fujinon is an APC-C lens, so it’s natural way of working is with APS-C body. But Nikkor is a full frame lens – in it’s case the natural environment is the full frame body. So why would I use it with APS-C body? Especially when the majority of the weight is concentrated in the lens? My observations are as follows: Nikkor + D810 shows slightly more details. But the question, for which temporarily I have no answer, is if this difference comes from the lenses or from the higher resolution of the D810? Please remember: 36 Mpx vs 24 Mpx. Second observation: Nikon much faster achieves focus – no doubt. And third observation: the Fujifilm set allows for much longer handhold use than Nikon’s. This is obvious: Fujifilm set weights 1870g, while Nikon set weights 3280g. The weight difference is 1410g. Seems not too much, but when you have to keep this over 3kg next to your eye simply you feel it and hands get tired quite soon. Unless you you are sportsmen, lifting weights 😉
So which one set to choose? If we need maximum quality, then D810 + Nikkor 200-500. But is the quality difference so big? It depends on what you will do with your photographs. I have printed photographs taken during horse racing on A3+ paper. Looking at these prints I couldn’t find any flows of quality, detail or any others. In case of large format prints it probably would be different (if you look at it from the close distance), and for sure the difference is visible when you look at 100% magnification on a big screen.
But when we need low weight, ability to easily move with the gear, keep taking shots for hours and still achieve high quality of the pictures, then the answer is Fujifilm. Especially when pictures will be used for viewing on the screen or to make A3+ prints. From my perspective I either print my pictures on the A3+ paper or put them on the web with the longer side of the picture having 1920 pixels. In both cases there is no visible difference between pictures taken with Nikkor and pictures taken with Fujinon. But I much more often take the Fujifilm set – for it’s lower weight (I can take shots all day long) and smaller size (much easier fits in the bag).
A side note: I totally don’t understand why Nikon offering excellent APS-C bodies, doesn’t offer APS-C telephoto lenses? The most natural connections are wide angle FX lens on the FX body and telephoto DX lens on the DX body.