Should I backup or copy [an Access database file]?
The "Back Up Database" and "Save Database As" options do the same thing. The only real difference is that "Back Up Database" will provide a default file name like



MyDatabase_2014-11-18.accdb


whereas for "Save Database As" the new name will default to

MyDatabase1.accdb


They both do what is essentially a "Compact and Repair" into a new database file. (The original database file is not compacted, only the resulting copy.)