Good windows design decisions
Windows registry: https://stackoverflow.com/questions/1616289/why-does-the-windows-registry-exist
Thinking about all the files with their bespoke customization, the registry seems downright elegant... although the ui for it is terrible and it is a scary thing
powershell: having programs produce *structured data* like ls, as opposed to text-only, which gets hacky very very fast when it comes to a processing pipeline
Open ecosystem: for example allowing Android apps to be run on Windows: https://support.microsoft.com/en-us/topic/use-apps-from-your-android-device-on-your-pc-07d3d029-236e-e71f-3561-d40d7491d435
And making ubuntu an app on windows. Without this I probably wouldn't be using windows right now
Postscript: good mac design decisions: ui is good, breaking changes are good (see Moxie talk about the ecosystem), emacs hotkeys everywhere is good, quality builtin apps including things like archive support built into the finder app. Things that are terrible on mac are disk image based installers, completely undiscoverable ui things like option-click notifications to go into silent mode, and shitty "user protection" styled features like "you can't open this app" "wait you clicked right click open? Ok now there's an option"