When comparing Flutter vs ASP.NET Core, the Slant community recommends Flutter for most people. In the question“What are the best ways to make a cross-platform application?” Flutter is ranked 8th while ASP.NET Core is ranked 11th.
Ranked in these QuestionsQuestion Ranking
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.
Pro Fast and getting faster
Ability to host on IIS, Nginx, Apache, Docker, or self-host in your own process.
Pro Built-in middleware
Pro Multi Platform
Can run on Windows, Linux and Mac (also Visual Studio Code editor).
Pro Ease of Use
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.