Which one is preferred, what are the benefits of using a report layout over copying an existing report, and how can a report layout be used?
If you copy a report, it becomes a completely brand new object with a new name and no reference to the original report. If this is called from an application you’d then have to customize the application to call the new application. If you use an application layout, it is still namespaced but has reference to the original report so you don’t have to change the name to all places the report is called.