iOS:
+ Swift
+ Less screen sizes to worry about
+ Less iOS versions to worry about
+ XCode is much lighter on resources
- Mac only
- XCode might crash every now and then
- Probably need an iOS device, as the simulator is very slow
- $100/yr developer fee
Android:
+ Kotlin
+ Studio runs everywhere
+ No developer fee
+ More stable IDE
+ Decent emulation
- Countless screen sizes to worry about
- Lots of Android versions to worry about
- $25 developer account fee
- Android Studio is resource heavy
- NDK requires lots of JNI boilerplate
Though, with all of this AR stuff, I'd just go the Unity/Unreal route, as it will probably be very game-y and such.