Advantage of adding react-native-firebase to Expo:
A1) React-native-firebase provides much faster performance (~2x) over the web SDK
A2) 27k npm downloads, Good documentation, as well as being active in the past year!
A3) Fully featured auto scaling backend for your users. That is what every entrepreneur wants. (scalable baas)
A4) Happier users like me or those who voted up! (Listen to your customers)
Issues with current web SDK implementation:
I1) It was designed from ground up for the web not mobile apps! ( For example: Firestore doesn't work on Android. )
I2) Since react-native is not their priority, it takes a long time to resolve react-native related issues (bugs)
I3) The Firebase Web SDK also runs on the JS thread, therefore potentially affecting the frame rate causing jank with animations, touch events etc.