Earlier quoted context omitted.
Would almost be a no-brainer if the Mac GPU wasn't a walled garden.
Is that any different from nVidia?
Nvidia cooperates with Khronos, implements open-source and proprietary APIs simultaneously, documents their GPU hardware, and directly supports community reverse-engineering projects like nouveau and NOVA with their salaried engineers.
Pretty much the only proprietary part is CUDA, and Nvidia emphatically supports the CUDA alternatives. Apple doesn't even let you run them.