Well, compared to 10.12? I'd say 10.7 or 10.8 were significantly better than 10.9, 10.10, 10.11, or 10.12. More stable, anyway.
Back before 10.10 or so, I used to just casually assume I could move my MBP from laptop mode to clamshell mode with an external monitor. Then I started getting kernel panics when doing that. Not always, just sometimes. So I stopped doing it.
And compare Server.app to OS X Server; it's not even close, Server.app is a buggy piece of crap by comparison. I was one of the people who was willing to pay $200+ extra for OS X Server. They took it away, I tried Server.app, and... it's garbage. The big advantage of OS X Server for me was reliability and ease of administration. Server.app breaks both of those, badly. Next time I do a home server, it'll just be BSD or Linux, because they do the job better.
More generally... I'm encountering more annoying quirks running Linux on a laptop than I usually had with MacOS on Mac hardware. Probably. But for actual serious bugs like stuff crashing or whatever? That's a lot more even. And if I don't like how it behaves, I can sometimes do something about it. MacOS has become much less friendly to me in the last few years. The number of things I was putting up with for lack of workarounds kept increasing. Sierra's new security stuff broke TotalSpaces, without which I find the Mac virtual desktop implementation pretty frustrating at best. (I do not like the animations. I want the new desktop to be fully done transitioning by the next vblank. I'm used to instant switching. Guess what MacOS doesn't offer?)
So basically, in terms of actual day-to-day experience of using the system? I don't think MacOS is really all that good at "less buggy". It's pretty good at a combination of "relatively stable" and "can run apps I care about". (The state of paint programs in Linux is atrocious.) But overall I actually get better stability from the other unixes.