I would recommend to use persons - it is explicitely there for representing single individuals in the system that do not need to have a login account. So you might have (don't know if you need that) authors that are not able to login but are entered by another user into the system.
You can later augment a person to a user by giving them an account. I think that's covered in the admin UI with 'select existing person from this system', but I'm not sure. If it's not there it should be easy to add a page for that.
Persons can also be associated with each other in groups, in case you want to model employees of different client companies or the like - it's not necessary to store them as users for that.
