When comparing Amber vs Flow, the Slant community recommends Amber for most people. In the question“What are the best solutions to "The JavaScript Problem"?” Amber is ranked 27th while Flow is ranked 32nd. The most important reason people chose Amber is:
Amber includes an integrated development environment with a class browser, workspace, transcript, object inspector and debugger.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Includes an IDE
Amber includes an integrated development environment with a class browser, workspace, transcript, object inspector and debugger.
Pro Smalltalk is a simple, elegant, and powerful language
Pro One-to-one JS equivalent
Amber is written in itself, including the parser and compiler, and compiles into efficient JavaScript, mapping one-to-one with the JS equivalent.
Pro Checks to see if you check for Nulls
Because getting those exceptions is just not fun and very pervasive.
Pro Versioned type definitions
Pro There is support in many code editors via the extension
For example, there is good support through the extension in Visual Studio Code, which is a good editor for TypeScript, which is a competitor to Flow.
Pro Babel extension for strip of type annotations
Thanks to the Babel extension for the output, there is minimally modified code that is understandable to the author.
Pro Statical analysing of JavaScript code
Statical analysing of JavaScript code without pre-making any changes to it. But supported annotation types by extending the syntax of the language.
Cons
Con Very few learning resources
There are very little learning resources for Amber outside the official documentation. Which may not be enough for beginners, especially people that don't have much experience in programming.
Con Weak base type definitions even for popular JavaScript libraries
For example, there are definitions for Gulp, React.