- Flutter renders the UI itself rather than using native components, so you get the same experience on both iOS and Android.
- Flutter uses Dart, which can be compiled AOT, rather than relying on an interpreter.
- Flutter is completely open source, tools, engine, all of it. You can go a long way down before hitting iOS platform code, for example, that you don't have source access for.
There others, but those are the biggies for me.