When comparing WebUI vs Flutter, the Slant community recommends Flutter for most people. In the question“What is the best CSS framework?” Flutter is ranked 25th while WebUI is ranked 29th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Scalable CSS transform and SVG shapes
WebUI includes scalable CSS transform shapes and scalable clip-path shapes.
Pro Supports build customisation
Build customisation allows components that aren't required to be excluded using SASS includes and grunt tasks.
Pro Full support for flexbox
WebUI includes a full range of flexbox classes, including breakpoint specific classes based on REM units.
Pro Multiple grid systems out of the box
WebUI includes a flexbox, a table, and standard grid systems. These grid types can be used in combination and together.
Pro Generic design
Every component is built to be generic and interchangeable. For example, there are no restrictions on where grids, containers, menu buttons, or dropdowns can be used.
Pro Powerful tooltip system
The tooltip system includes viewport boundary collision detection, auto positioning and auto sizing for small viewport areas, configurable boundary margins, and many behavioral settings, such as focus, hover, static, nohide.
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.
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.