Yup, gonna have to agree with that. Buy whatever your software requires.
The software I use on a daily basis is available for both MacOS and Windows, and I have both, and don't feel strongly about either of them--they've both got their pros and cons.
Apple hardware is well-built and has a price to match the fit and finish. You'll find that most Windows computers of similar quality come at a similar price--the only difference is that Apple doesn't compete in the low-end of the market.
Lets say for the sake of argument that MacOS is inherently more secure than Windows. It's not going to matter, because you'll be using Windows to run your tax software whether that's in a VM on top of MacOS, or running natively with BootCamp.
I will say that it's more common for Apple users to evangelize for them, and I think that mostly has to do with Apple not playing nicely with others. You can't use Facetime or iMessage on Windows or Android, for example, because part of Apple's business model is to keep their users trapped within their ecosystem.