Competing isn’t really the target. V-Ray is a great engine, and if you want to use it you should. That said I don’t know if it is available for Rhino for Mac, or if it’ll be available for Rhino 6 on the Mac when we’re done. Regarding render quality I guess it is up to you do decide. https://www.cycles-renderer.org/ shows results with the engine. You can also browse the Blender community forum over at https://blenderartists.org to see work created with Cycles as the engine.
There is a great potential for materials, but it requires currently the geeky approach via the
Cycles XML special material combined with
GhShaderNodes in Grasshopper. With that your imagination is the limit.
OpenCL should work with AMD hardware. I have been unable to get the CUDA hardware working in our office, so that is still in limbo. Once I can get that running, I can fix and test Raytraced with Nvidia hardware. In theory it is great - in practice you are currently limited to CPU and AMD GPU.
See answer to item 1
edit: moved to #serengeti:mac since this is about the WIP version.