I have modified the subject of your post as 'NetBackup' in a NetBackup forum does not give any indication of the real query.
About Azure storage - I would look for guidance from Microsoft.
I found the following:
The Blob Storage account is a specialized storage account used to store block blobs and append blobs. You can't store page blobs in these accounts, therefore you can't store VHD files. These accounts allow you to set an access tier to Hot or Cool; the tier can be changed at any time.
The hot access tier is used for files that are accessed frequently -- you pay a higher cost for storage, but the cost of accessing the blobs is much lower. For blobs stored in the cool access tier, you pay a higher cost for accessing the blobs, but the cost of storage is much lower.
So, the choice that you make all depends on how often you will perform restores.