Site Collection Administrators defined from Central Administration and from site collection top level site

As you know when creating a Site Collection from the SharePoint central administration you can specify Primary and secondary site collection administrators. And these two site collection administrators are added automatically in owners on the top level site. Central administration limits you to add only two site collection administrators, if you want to add more site collection administrators, you can add them from the site collection top level site.

Now the common question is:-

What are the differences between the site collection administrators as defined in central administration and site collection administrators as defined in site collection itself??

Here are the differences:-

Site collection administrators defined from the Central Administration receive email notification including quota and use confirmation messages. Site collection administrators defined from the site collection do not receive those email notifications.

When you change owners by using Central Administration, the list of site collection administrators will be updated automatically. However if you change site collection administrators from the site settings of the top level site, changes are not always reflected in the owners properties for example:- adding a second site collection administrator to the site does not make the user secondary owner.

The best practice is to use Central Administration to manage the primary and secondary owners as they are automatically site collection administrators and receives email notifications.

Note: Both sets of site collection administrators defined from Central Administration or from the site setting of top level site have full control permission to the site collection.