Are you looking at a mount operation? In that case you would need to select the snapshot with "_backup" suffix. The exact steps are available in section 5.8 of the SMHV Best Practices Guide. Here'e the location for that:
The two snapshots are created in response to "auto-recovery" done by Hyper-V VSS writer during VM backup.
Hyper-V writer creates a software of snapshot of all the VHDs inside the VM (using system provider). This is captured in the first snapshot on the storage system. The applications and OS in the VM is not frozen when the snapshot is created on storage system. So, later, VSS asks us to mount the first snapshot and the writer then does auto-recovery to revert the hardware snapshot to the software snapshot taken earlier. When auto-recovery is complete we take the second snapshot (_backup suffix).
Hence, the second snapshot should always be used for "connect" operations. The different between the two snapshots is essntially the auto-recovery changes.