Integrating the Private Message module with the Message module

I'm the maintainer of the Private Message module. For version 2.x of the module, I've integrated with the Message module, by creating a new Message entity upon the creation of a Private Message. One of the users of the module asked about using Message entities instead of Private Message entities, but I think that Private Messages are a specific sub-set of messages, and therefore I think that if anything I'll extend the Message entity class with the Private Message entity class, but declaring it as a separate entity type in the comments, so that Drupal sees it as a separate entity, that also gets the benefits from the Message entity.

My question is, is there any benefit in doing this? Or do you see a benefit in keeping the Message Entity and Private Message entities as entirely separate entities? Any other thoughts you have would be appreciated as well.