Advantages
You require less backup accounts
You can use one username and password to configure the backup setting for all Backup Sets

Disadvantages
You must use different backup sets for different computers

Whenever a new backup set is created under the backup account, you need to go back to all computers using the same backup account to uncheck the “Run scheduled backup on this computer” option for the new backup set (Since backup setting is saved on server and new backup set is default to run on all computers, i.e. with the option checked).

Improper configuration could easily cause problems, which are difficult to debug.