the two best things for me about the MacOS are the integration with other apple devices/services and that things "just work". When I first started using it after using Linux for years I installed Thunderbird and the like. Now I use the Apple programs (Safari, Mail, etc). There are a lot of little niceties in things like Preview. I don't generally use Siri though.
The way it integrates with my other Apple devices, that it does point in time backups automatically, how well it suspends/resumes, long battery life - these are the killer features for me. For instance if my iPhone is in my pocket and I visit a site with SMS based 2FA the computer gets the code from the phone and offers to paste it into the prompt. There are a lot of little small things like that. A lot of them would involve using the Apple ecosystem, like Apple Music, iCloud, other apple devices, etc. Just my .02.