Hardware, period. AMD's hardware suits better in DX12, better compute throughput, hardware scheduler. Has lower latency in DX12, Vulkan and in turn also Virtual Reality (if you care about that).
If you didn't keep up, recently (well over 6 months) found that Nvidia's hardware can NOT support asynchronous compute despite being advertised that. It has no proper scheduler so it relies heavily on the software to do so which impacts performance and frame latency. Ashes of the Singularity's implementation of DX12 shows performance increase with AC on on AMD hardware and performance decrease on Nvidia's just because of these differences while DX12 shows performance increase (small or big) on every card when AC is off, so don't say this is a bad implementation. Hitman's DX12 shows the same thing.
To illustrate (well link images).
This is the 980 Ti's frame time in VR.
This is the 960
This is the 380
And this is the Fury
One of the strongest card has relatively the same (if not worse) frame time as a mid low end AMD card and the Fury just stomps it.
And this is consistency.
AMD's
Nvidia's
*looks at the 970, 980, 980Ti, Titan X coil whining threads in google*. Okay.3. Coil whine. Go look at reviews of all the current amd cards, almost none of them are 5 stars across the board, the reason for this is you have a spattering of negative reviews on almost all of them with people complaining of coil whine.....this is unheard of on the nvidia side.