Both Flutter and React Native are popular frameworks for cross-platform mobile app development. But Flutter is easier to use as it is more resistant to system updates. And React Native depends on native elements, so when the update is released, some problems may appear in the launch app.
The React Native uses JavaScript. In particular, React JS is a JavaScript library for building user interfaces. With Flutter that use Dart a programming language created by Google.
React Native enables the communication between JavaScript and the native language via the JavaScript Bridge. And the Flutter doesn’t require a bridge to communicate with native components. It has everything packed within itself, including frameworks like Cupertino and Material Design.
The Flutter if your budget is limited or you need to make a simple application quickly. Also, you can make a Flutter application if UI is core for your app. But if your funding is sufficient and you want to create a complicated app, go with React Native.