Is there any advantage when using File Backup compare to Category Backup? Size of backup is not a concern!
File backup will be a more comprehensive backup allowing you to select whatever files needed to be backed up.
Category will pick files for the categories selected and will not be as specific.
For more information, please see the link bellow:
How to create a category backup using WD SmartWare
How to backup specific files and folders using WD SmartWare Version 1.6.x and earlier