Our 'Amazon - Create Server Snapshots' task will take snapshots of all volumes attached to a server, whereas our 'Amazon Create Volume Snapshot' task will only take a snapshot of one individual EBS volume.
So the 'Amazon - Create Server Snapshots' task takes one snapshot of all drives related to the Instance Ids. (See Below)
The 'Amazon Create Volume Snapshot' is just the snapshot of a single EBS volume, where you select the individual Volume Id. (See Below)