roles and permissions for membership website

I have a site which utilises 3 types of users, an "admin", "employee" and "employer".

I'm trying to understand if I now create a "paid" membership for the "employer", which has added feature over a now "free/standard" employer whether they should be seen as two different roles OR just different permissions.

Using Laravel Entrust Roles/Permissions.

I would appreciate justification why one over the other, or when is the tipping point to use one over the other, alternatively another way all together. I have not been able to find a definitive answer.

via Chebli Mohamed