What benifits does Backup manager provides in 12.5 version?
Since Plesk 12.5 it is possible to create incremental backups. It allows to reduce the backup creation time. In this case there is might be small disadvantage in speed upon restoration.
There is improvement in process of backing up data to FTP storage. It is required as much free space on the local storage as a backup itself consumes but not doubled as previosly.
NOTE: Find more details in official Plesk 12.5 documentation .