As far as I understand a data scientist should learn both Excel and Bash. And the golden mean is this case is Mac OS, because it has both. And later I can install Ubuntu on Macbook.
You will not find the most suitable OS for data science. It will come down to preference and what tools you will use. Data science is broad, what tools people work with will vary, some will have support in one OS and less in another.
All OSs are suitable and used by data scientists. Often you don't get to pick yourself. But very few things are exclusive to one OS, so it all works out. I would say you should pick the one you are most comfortable with. You want to spend more time learning data science and less time learning a new OS.
First of all, welcome to the data science Stack Exchange.
You should really use what you like. Half of my colleagues use Linux, the other half including myself OSX. It really comes down to what you are familiar with. For me, OSX provides a good balance of good user experience while still being easily able to work with bash and use all of the features of UNIX based system. Also, the MacBooks are a great build quality, but a quality which is kinda pricey.
I have also installed Debian on my MAC as a dual boot, however, I have not started it up for the past few months. It is really hard to find any tool which does not work on OSX.
You can use pretty much any system and computer to do DS.