purpose built backup appliances

I think you may have made a typo error:
"what is difference between PBBA 5230 & PBBA 5230".

Maybe you meant 5230 and 5240?

The NBU Appliances is a master and/or media server with local storage all in one. It supports all the latest dedupe technology, like source and target dedupe, accelerator, etc.
Lots of documentation about NBU Appliances over here: 
https://www.veritas.com/product/backup-and-recovery/netbackup-appliances/resources

In short - the 5240 is the latest generation of NBU Appliances, replacing the 5230.
It is faster, smaller footprint, more energy efficient, etc. 

The Hitachi Appliance is a 3rd-party backup appliance that still needs media servers and can only perform target dedupe.

You can also read the last 2 replies in this post as both are 3rd-party OST appliances: 
https://vox.veritas.com/t5/NetBackup-Appliance/Dell-DR-600-appliance-integration-with-Netbackup/m-p/828406

The features supported by each type of dedupe appliance can be found in the HCL (see the post that I have mentioned above for URL).

I have more experience in NBU 5230 working with Hitachi Protection Platform S2750..Please let me know if you need any specific questions to be answered. It has been working good in our environment.