OSX is at least predictable and therefore from a developers perspective it is arguably stable.
Linux is fine for developers as well.
But for users, it doesn't help if you bought a tool last year and it gets non functional because Apple removed or tightened down a function in their OS.
You can only hope than that the developers are still around and update it if that's even possible.
Microsoft is backwards compatible to an insane degree. Which gives you stability but not consistency.
OSX is consistent but Apple throws out backwards compatible features every other year, so not really stable.