RE: Main Difference Between Security Roles
I guess I have the answer on this as I was searching for an explanation for those two roles as well:
If your're using any Dynamics 365 Module (except Marketing), lets say Sales, then you will get the "Marketing Manager" and "Marketing Professional" Roles with all the other standard roles. This will give you privileges on the little Marketing area in Sales.
If on the other hand you have the real Dynamics 365 Marketing you will get all the standard roles as well (e.g. Salesperson as well) BUT you also get "Marketing Manager - Business" and "Marketing Professional - Business" on top and those are to use inside Marketing to have sufficient privileges for the functions.
Microsoft somehow points this out in the documentation but only in a side note that's not very helpful: learn.microsoft.com/.../admin-users-licenses-roles