SharePoint's default navigation requires that each Site Collection display unique navigation. Having different menus based on each Site Collection makes finding content confusing for users. Mega Drop Down content can be displayed from any Site Collection or Web Application.
Menus can be configured to share navigation across collections allowing content to be managed from a single location. When you update the navigation in Mega Drop Down, the changes are immediately available to every site collection and web application—without the need to synchronize or duplicate content.