Use full export the first time you need to copy an application to another system. After the first time, delta export is recommended, because it includes only the objects that have been changed, and therefore reduces the size of the file.
Use full export for a complete backup of an application.
Partial export is recommended only for exporting one or a few individual objects. It’s not recommended as the normal method of exporting voice application objects: to ensure the integrity of your applications, use delta export instead.