Off the top of my head for ios - push notifications, offline use, optimized storage options (local storage not cleared after 7 days of no use), app-like ux (no browser controls), home screen icon for easy access, background audio (sound while app is closed).

The real advantage is for devs who can build an app that feels like a native app, but with one codebase for distribution across OSs/devices, not having to pay the apple/google tax, and not dealing with app review.