Purely on monitors, I've had the opposite experience - Windows has been dramatically buggier and worse-behaving. Particularly if they're different DPIs - Mac DPI support is just so far ahead of Windows that it's absurd.

I've had slightly better luck getting monitors to work at all on Windows... by a single monitor. I mean more around system behavior when I plug in a monitor. OSX acts... normal? Stuff moves where I last moved it in that setup, or stays wherever it is. Everything stays about the same physical size. Display-rearranging is easy and perfectly reliable. On Windows, literally anything is possible, often including windows completely disappearing or going completely out of the bounds of any screen.

That said, I have no idea why monitor support is so buggy anywhere. It seems nuts. Is it actually that hard? I get that there are some scenarios where there are no perfect choices (e.g. what do you do with desktop icons / window positions when changing sizes? they've gotta go somewhere)... but the amount of times Windows has shoved windows completely off-screen and made them inaccessible is totally inexcusable. It even does that when going from a small screen to a large one, or just adding a second monitor. What kind of code leads to that??