Advantages of federated Exchange backup against passive-only backup?

We have a two-server Exchange 2013 DAG that we back up with Avamar's Exchange VSS plugin, but individually instead of via the DAG client.

What is the difference between a federated backup of Exchange as opposed to just telling both servers in the cluster to back up their passive databases? In one case both servers can be set to run their backup at 8pm. In the other case the DAG client can be set to run its backup at 8pm. In both cases Avamar is only backing up the passive databases, so I fail to see what advantage(s) using the DAG client gives us, other than only having to manage a single Exchange VSS backup instead of two.

Thanks.