I just like to add that if you are going to use Storage in Android, there is no reason to think on GCP storage, Firebase is the way to go because of Sam's first bullet point.
However when working with python functions I prefer GCP API's because it gives me auto completion in VS Code where Firestore for python won't.
In the end Firebase Storage is the same as GCP Storage but Firebase makes it really easy to work in Android with GCP and the same for the rest of API offered by Firebase.
I started using plain Firebase, but I have come to get more familiar with GCP as some needs were not covered at some point(like Scheduler, which I think now is available)
Edgard Ochoa