It depends a bit on what you are doing, as Helvetosaur already mentioned there are way more plugins available on Windows than on Mac. If you need some plugins that are only on Windows then Windows it should be.
If I remember correctly Rhino started as an AutoCAD plugin before it became (fortunately for us) a standalone program so it’s origins are on DOS/Windows but I don’t think that these days there is much difference between Mac and Windows when it comes to Rhino itself.
Something else to consider is graphics card support, if you would need a Quadro card for your (other) software then Windows is these days basically the only option because the M1 etc. processors have their graphics built in due to their architecture.
Performance wise the latest higher end AMD (Ryzen 7 and up) and Intel (i7/i9 and up) processors are very close to the M1 processors, when the M2 processor arrives we’ll find out if they will still hold up.
With Mac you are “limited” to what Apple offers, with WIndows you can have a tailor made system made.
Windows might be a bit or a lot cheaper than an M-series Mac depending on specs you want.
I would suggest to choose based on what fits your use and software scenario/availability, appeals to you moer and what you are willing to invest money wise. There is really no right or wrong in the general sense, it depends on the details that matter to you.