vShield Manager backup via snapshot?

Is it possible to periodically backup vSM 5.1/5.5 with snapshots?  On one hand VMware recommends to use the vSM's internal data backup/restore mechanism. On the other hand VMware recommends to take a snapshot of the vSM as Upgrade Prerequsite: 'Take a snapshot of vShield Manager so that you can revert to it in case the upgrade fails.'

Does anybody know restrictions or disadvantages (besides higher disk space)  for using vSM snapshots as periodic backup (together with other VMs)?

Thanks

Michael