Directory DNS Domain domain_query

Addon domain is dependent in main domain

Addon domains is dependent into your main domain name if you main domain i close then the whole addon domain suddenly clapse  or down or suspended but the directory of each domain is safe because it is in the sublevel domain specially when you add more scripts or editing codes.

The advantage of using the parkdomain is it belongs to the top-level directory even if your main domain is close still your website runs because it is not dependent on the main domain.