Please find to the point conclusion about the both, it took time to understand me but be clear by following analysis.
Below things are only about Site Collection Owners
- Are controlled via `Central Administration | Application Management | Change site collection administrators’
- When you create a site collection, Windows SharePoint Services automatically lists you as the site collection owner.
- You must have at least one and maximum of two owners and they become both “Site Collection Owners” and “Site Collection Administrators”
- Both must be users (groups are not allowed)
- Will receive email in case of e.g. quota limits reached, or site not being used (this is configured by Farm admin)
- Site collection owners and secondary owners are also site collection administrators. However, owners and secondary owners are the only users who receive e-mail notifications for events, such as the pending automatic deletion of inactive sites. By default, site collection owners also receive requests for access from users who have been denied access. A user who is a member of the Administrator site group can use the Site Administration pages to change the e-mail address that receives requests for access.
- If you remove a person who is “Site Collection Owner” as part of modifying “Site Collection Administrators” in Site Settings in the Site Collection he/she is removed from “Site Collection Owners” as well. If it’s the Primary Owner then the Secondary Owner becomes Primary Owner, if there is no Secondary Owner, the first user in the list of Site Collection Administrators become new Primary Owner
Below things are only about Site Collection Administrators.
- Are controlled via Site Settings | Site collection administrators
- Have full permissions in the site collection
- They can view, add, delete, or change all content within those sites as well. They can add and remove users from sites and send invitations to those sites
- Can be users or groups
- Configured via Site Collection administration not from SP Admin
Note: The————– Owners group of a site (THERE IS A OWNERS GROUP IN YOUR SITE GO TO SITE LEVEL PERMISSIONS IT IS ON THE LEFT PANEL) is not the same as the site collection owners(SITE COLLECTION OWNERS IS NOT IN THE SAME PLACE OF YOUR SITE LEVEL OWNERS GROUP, YOU WILL NOT FIND SITE COLLECTION OWNERS IF YOU GO TO YOUR SITE LEVEL PERMISSIONS YOU WILL NOT FIND A GROUP FOR THEM, CAN NOT BE SET THERE), which themselves are called site collection administrators in the Central Administration(NOW, THE SITE COLLECTION OWNERS ARE CALLED ADMINS IN SP ADMIN) user interface, even though site collection owners receive email notifications that the site collection administrators do not