For which operating system is it better to build the mobile app first? (And why?)

I'm doing research on which OS is worth making an educational app for, and jotted down some pros/cons for both iOS and Android.

Android:

– It is known that there are more Android users, so you can potentially have a larger testing/user base.

– You don't pay any fee when publishing an app on the Play Store.

– The opposite is that Android is used by different devices, so optimisation can be difficult.

iOS:

– iOS users are more willing to pay (and I'm already used to iOS).

– The disadvantage is recurring payments in the App Store every year (about $100).

Several people have advised me, for example, the Ionic Framework or Flutter, which would allow for cross-platform development.

From your point of view, which platform is worth making an app for?

Do you know any good alternatives to Flutter and the Ionic Framework?