When comparing Flutter vs Xamarin Forms, the Slant community recommends Flutter for most people. In the question“What are the best systems to deliver native Android and iOS apps from one code?” Flutter is ranked 1st while Xamarin Forms is ranked 4th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Open source
Pro Great developer tools debug/hotreload/analyser
Pro Based on Dart language
Dart is a Java like language, easy to learn and startup fast for millions of Java developers.
Pro A single codebase for iOS AND Android
Pro Fast
The developer's goal is to allow people to make apps running at 120 FPS.
Pro Many tutorials online to start learning
Pro Supports F#
Xamarin supports F#, giving developers a functional language for building native apps on iOS, Android and Windows.
Pro Free
Microsoft bought Xamarin and made it free.
Pro Cross platform
Cons
Con Still in development
According to the website, Flutter is still in its early stages of development.
Con Based on Dart language
Dart is a Java like language, easy to learn and startup fast for millions of Java developers. BUT if you have to learn it ... it's a con.
Con Dart is unpopular and never gained serious community traction like Kotlin or Java
Con Does not support 32-bit iOS devices
If you plan on targeting iPhone 5, 5C or earlier, you can forget about Flutter.