So I checked out NVIDIA's RTX Ray Tracing technology, and I have to say it's pretty impressive. Its advantage is it can be implemented in supported engines. However I do believe that its limitation on Volta is for their preliminary demo, and I do believe that some optimization is still in the works to get it to run on Pascal, and at most Maxwell, since they know that most users are on one of those two architectures anyways, and what sold Pascal from the beginning was its monumental performance jump compared to Maxwell.

Compared to Radeon Rays, AMD claims it has similar results, and they've stated that it can be ran on any hardware, but I really doubt its adoption rate compared to NVIDIA RTX due to technical support and resource allocation, despite the former being open-source middleware. I still think the latter will get much better adoption rates thanks to the tech support you get, and development resources to further enhance scalability and performance. 

But I still think the Brigade Engine from OTOY does it better, as that engine's ray tracing tech can be ran on two GeForce GTX TITAN cards for 1080p 60 FPS, and it is full scale, rather than being limited to reflective objects, shadows, and transparent objects. But if I have to choose between Radeon Rays or NVIDIA RTX, I would pick NVIDIA RTX because of its scalability, performance, and the most important feature of all: technical support. Recently, I've filed a few tickets to AMD for some help with their Radeon ProRender, and they've never replied to them in a timely fashion, so I am in limbo, and therefore I discontinued using Radeon ProRender, and went back to Cycles for blender, and Arnold Renderer for Autodesk 3ds Max and Maya.