When comparing Lightweight Native UI vs Flutter, the Slant community recommends Flutter for most people. In the question“What is the best approach to mobile app development?” Flutter is ranked 4th while Lightweight Native UI is ranked 6th.
Ranked in these QuestionsQuestion Ranking
Pro Write once, run anywhere
The portability of this solution often exceeds even HTML5 since it isn't limited by browser fragmentation.
Pro Native performance
Solutions often use low level graphics API's optimized for native games to produce the performance level of games while compiling the application to native.
Pro Deep customization and control
These solutions usually allow the developers to customize every aspect of the app to the finest details since everything is rendered by the solution
Pro Doesn't depend on OS whims
OS providers often change widget themes and behaviors on whims causing incompatibility and breaks in design/code. This isn't as much of a problem in such solutions.
Pro Ability to access native functionality
Solutions in this space can still call native code directly and sometimes even embed native widgets in place
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
The developer's goal is to allow people to make apps running at 120 FPS.
Con Non-native look
Such solutions don't always have a 100% native look, these can range between not at all to "almost there". Some applications can provide a feel that's superior to native functionality.
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.