Most people would say that PostgreSQL gives you the same portability that you have with your app, but at a different level. You can port your PostgreSQL database from a Linux server to a Windows server and back again and your application doesn't care. But because you are porting at the db layer, your application could leverage a bunch of PostgreSQL features that are very useful. As a developer, this might not matter a lot to you, but as a company, who relies on its data and expects longevity from its systems, this kind of thing matters a lot. PostgreSQL is a technology that you can rely on in the long haul and you will not be held hostage to a technology owner whose interests are not aligned with yours.