as am starting with the rhino and also at the same time am looking for a upgrade for my pc which will be OS will give me the best results MAC or Windows
I think it comes down to two things: which operating system you prefer, and which Rhino or Grasshopper plug-ins you rely on. In terms of Rhino itself, it is pretty much as good on macOS as on Windows (as far as I can judge). Some plug-ins and add-ons are Windows-only, though.
I use macOS with Rhino 8, and for my work in architecture (job) and object design (hobby), it’s a satisfying experience. However, I do not use many plug-ins.