There are three main downside to Progressive Web Apps (PWAs):
Support for PWAs on iOS is still incomplete and somewhat buggy. This means that PWAs are still not the cross-platform solution we would like them to be. For iOS, at least, you may still need to implement a native app.
Even on Android, which has the best PWA support, there are still some device capabilities which are either not accessible from a PWA, or the experience is less friendly to the end user.
All that said, transforming an existing website into a PWA is generally fairly straightforward, and loses you nothing. Thus, I generally recommend that you try to go for it.
Hopefully above guide will help you if not follow our blog on Progressive Web App Development Company.