My profession requries
competence with whatever OS my clients use.
Here are the plus and minus points I've seen over the last 20 some years:
MacOS:
Since Carbon (OSX) stable, easy to configure, easy to use, Unix based, runs on non-apple hardware (not quite with apple's blessing, but it works perfectly). Security issues are not as pervasive as Windows.
Not so good: The mentality of some appleMac fans is enough to make you want to run screaming back home to Billy G.
Support is awful, worse than awful, just plain horrible when something does go wrong and there is still a hard core of people using MacOS who haven't got the first clue how to work with other systems. Security issues get overlooked and people who dare to raise them get bashed. The two times students have broken into our databases, it was through those "there are no worms, trojans or viruses which can attack us" Macs in the prof's common room. Guess they forgot to tell that to the USB sub-system.
Linux:
A distro like Ubuntu 7.x or above will change your mind totally about using Unix derivatives. Fast, forgiving, safe, friendly, free. Secure as MacOS and linux users tend to observe basic safer computing guidelines which neither Windows nor MacOS folks even know exist.
Unfortunately, some things are still a bit dodgy. I haven't actually had to write code to do anything harder than an Office macro for Windows in decades, with Linux, unless your hardware is supported 100%, you will need professional help or have to know how to program a work-around yourself.
Solaris:
This is what I use at the University when I have a choice between it and MacOs.
Heaven on Earth, as long as the applications you need are supported. Otherwise, fuh'gid'abo'it.
NT: (Windows NT, 2000, XP)
Anything from NT4, SP3 through NT5.5 SP2 is universally supported, more stable than MacOS, there are apps. for everything, even ancient hardware is supported and it just works.
Downside: Well, let me tell you a story. A long time ago, the Feds decided that Microsoft was too big. They tried to split the company into two companies. Windows, run by Bill Gates. They finally found a potential buyer for Office, a nerdy woman with big hands, square glasses and big adam's apple named Gale Bates.
I don't mind, I like Ikea and Chevy. But for some, especially those who fancy themselves a cut above, Microsoft is just too, too, well, plebian.
Windows 6:
Whether you call it Vista or Mojave, there is no upside, just a seemingly endless list of downers. Try it, you're bound to discover some new bugs. Sort of like a major disaster in progress.
Ick.
Windows 7 (NT7.x)
So far, so good - and it runs fast and stable even at this early stage on my little Netbook (Acer AspireOne, 1.5G Ram, 160Gb HDD). With Aero.
I think Microsoft might have finally got it right.