The phone is a poor place for business rules. The app shows and collects. The server decides permissions, stores the record, and talks to payments.
When an app is the right tool
Repeated work away from a desk: a driver marks a delivery, a technician photographs a site, a client checks status without a browser. If someone opens the product once a month at a laptop, a responsive web app is usually enough.
One product, two stores
One API for iOS, Android, and the web. The clients differ in screens, not in rules. A shared codebase fits when the interface is the same and you are not pushing platform-specific graphics. Keep native pieces for push, camera, location, and the offline queue.
Offline is its own design: which actions pile up without a network, and what happens if the server record changed meanwhile.
Example
A technician app: today’s jobs, photos, a “done” status, the client’s signature. Without a signal the photo waits and uploads later. Dispatch sees the same status in the web console because there is one source.
Store accounts, review, and updates are part of the estimate, not a footnote.