Userbase dev here -- yep, biggest difference from both being that user data is end-to-end encrypted with the user's password by default.

Compared to Parse, we offer a simple SaaS product.

Compared to Firebase, we have a much simpler pricing structure.

Considering how early on we are, we also have the benefit of being much simpler to start using (fewer features/options to wrap your head around and configure) :)