Its a big advantage for Flutter now as Apple jumps on the train of declarative UI programming as it is available to every smartphone platform already whereas SwiftUI won’t be available until fall and then for iOS 13 only. So it may be reasonable to do it the other way round: start with Flutter now and if it does suffer the fate of so many frameworks which have one good year or two you will have acquired the skills to switch to SwiftUI by then. Dart is not so hard to learn, if you know Swift Dart is just a variation lacking some Swift features. And with easier memory management due to its GC adoption.

Now what about Android? It comes from Google like Flutter does. When will Android get declarative UI? Google pushes Kotlin as the new primary language of Android but Flutter is based on Dart — will there be a Kotlin version of Flutter? Is there a discussion going on at Google wether the success of Flutter and Apple’s move renders Kolin (along with everything JVM-based) mood for Android?

I guess this year will be exciting. But eventually the platforms need consolidation: it is not that much fun to learn a new framework and/or programming language every year. May evolution leap forward for some time but let it settle down after that.