Hi there,
Note is the flexible/dynamic tagging. Tag itself is static.
My idea is that sometimes you need to make it flexible to change the status of the file or note, such as “do it now” or “later” in this case it is more convenient to use the note system which you can drag and drop to a new place. To use tags it is more cumbersome to remove the tag (such as “do it now”) and add another one (like “later”).