Ranked in these QuestionsQuestion Ranking
Pro Native feel
Sencha Touch is well known for its ability to provide a native app experience through it's native-like themes and widgets.
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 Open source
Pro A single codebase for iOS AND Android
The developer's goal is to allow people to make apps running at 120 FPS.
Con Commercial and expensive
Sencha Touch is targeted towards enterprise-level development, and the price tag reflects that.
There are many different product options available by Sencha. Most licenses start in the thousands of dollars, and require a minimum purchase of 5.
Con Still in development
According to the website, Flutter is still in its early stages of development.
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.