For most people, there would not be any benefit by creating multiple data collection policies.
There are situations where you could benefit from having one policy for certain devices and another policy for other devices. An example would be that if you had a number of large arrays that required more time for collection, you could change the data to be collected every 72hrs rather than 24hrs for everything else.
You could also collect data more frequently for specific devices that you wanted data to be more current.
Basically, it is only helpful if you need to collect data for some devices at a different frequency than others.
I hope that this is helpful.
--- Mark Butler Micro Focus SW Support Engineer https://softwaresupport.hpe.com/