The chief difference is that Micro$loth OSes are NOT open source. G**gle's Android Open Source Project (AOSP) & ChromiumOS are Free and Open Source (FOSS). Which leaves individuals and businesses free to modify them, remove all of G**gle's spyware and crapware, and market them as their own.
Point of fact, there are successful 3rd-party Androids available, such as LineageOS, CalyxOS, and (the aptly-named) Paranoid Android.
So if G**gle remains true-to-form, if they produce an Android OS for desktop, they probably will also release an FOSS generic derivative as well, that can be used without completely surrendering your privacy to Debil G**gle.
So game, set and match, G**gle.
https://en.wikipedia.org/wiki/LineageOS
https://en.wikipedia.org/wiki/CalyxOS
https://en.wikipedia.org/wiki/Paranoid_Android
Excellent points. Thank you.