According to some of the people who make Octane Render, they said they had a meeting with AMD and that AMD is dropping Open CL support. They also complain about some things I don't get. I don't know what Otoy's problem is with AMD's GPGPU stack and drivers, and I have no idea what "Boltzmann" is.
https://render.otoy.com/forum/viewtopic.php?f=30&t=59213#p303235
I know Otoy's been trying to get their product on AMD hardware for some time. I have no idea how reliable they are as a source for this type of thing. They haven't shied away from complaining about AMD before. They've been quite direct (and perhaps a little dramatic) about issues with AMD in the past, only to turn around and say everything's OK again a few months later. The only thing I take away from this is that they don't complain about nVidia this way.
Don't take this as gospel. Take it as more gossip and/or use it to inform any hardware purchase decisions if Octane Render is a must for your workflow. If you spend all day in Final Cut Pro, this probably will have little effect on your decision to stay with Apple or not.