We have implemented both, one of our organization concerns is Apple IDs that was previously enrolled on a iOS mobile device we no longer have access to. Case in point, our email naming convention is "First Letter of the First Name" and the "Full Last Name" (ex. jsmith@companyname.com) but if that Apple ID needs to be recycle with a new employee Apple ID with the same naming convention, we are force to add a number to the email address when registering an Apple ID and therefore is force to add that same email address as a aliases on the back-end to that particular company account. Also take into consideration, that we are just now implementing Jamf and ABM but prior to that, we was manually advises users to use their company email address to register with their Apple IDs. So as a growing organization, we see that kind of getting out of hand and inquiring the best practices on managing Apple IDs.