Difference between FCM and APNS

• FCM is sent as JSON payloads and APNS sends either string or dictionary.
• FCM has a payload of 2KB while APNS has a payload of 4KB.
• APNS saves 1 notification per App while FCM saves 100 notifications per device.
• FCM supports multiple platforms while APNS requires their proprietary platform.
• Acknowledgment can be sent in FCM if using XMPP, but it's not possible on APNS.

Advatage of FCM

• Even if the user disallows notification, you can notify your app if the app is running in the foreground (using shouldEstablishDirectChannel).
• Don't need to create dashboard to send notification on the device.
• Notification analytics on FCM Dashboard.
• Easy to create notification payload structure.
• App Server side handling is easy, Only one key is required for multiple apps and platform (iOS, Android, Web)