MacOS for multiple desktop computers and laptops.
Being a writer, the multiplicity of brilliant writing and outlining software for Mac OS has simply made this a no-brainer for...well, for decades.
iOS for iPad (obviously) and iPhone. Here again, the Mac ecosystem in my experience tends to be simple, organic, and never 'gets in the way' of what I need to do or want to do.
In terms of power and flexibility, the MacOS systems run circles around iOS but that's another story.
Being an ancient (early adopter) Nerd from the dark ages, I have also used Windows PC's (mainly for computer and video games, which for a long time were superior on Windows machines than Macs), but finally gave up because of the endless viruses which always seemed to periodically infect and or destroy whatever Windows machine I was running. Macs are not completely immune to viruses etc. but in simple real-world terms they are superior in my experience in the sense that they almost never get infected the way my ancient PC's once did.
I actually used MS-DOS and CP-M operating system machines before my first Mac back in the 80's which I think dates me. At the time, both CP-M and MS-DOS were so much more technically oriented and (for technophobes) daunting than the early Mac systems that it was like different universes. Today, the latest iterations of Windows OS's are actually very similar to the Mac OS's of the last decade or two, so, honestly, the differences today aren't what they once were.
As an ancient and brilliant friend once advised me - the best computer and OS to get ... is the one which does the most things you want or need it to.
Words to live by...even decades later.