The page Migrating Confluence between servers recommends copying over the entire contents of CONFLUENCE_HOME directory to the new server.
And yet, Confluence also has a seemingly more lightweight process to Restore a Site that consists of restoring from a plain XML backup.
Why is it preferable to use the full CONFLUENCE_HOME for migrating Confluence Server to a new server, versus restoring Confluence using the XML backup on the new server? What are the functional differences between these two approaches? What is the downside of migrating Confluence to a new server using the Restore a Site/XML backup procedure?