Android one device have stock Android, doen't have justers and other navigation settings.you got 9gb Android fast but stock. Miui have more custom settings.
my old phone is A2 lite and I never back to Android one. you use miui if change you lose so much buy Mi9t(redmi k20) global version.
A3 is good phone but stock Android I doen't like,is you chose.now I use redmi note 7.