Typescript is older (2012 vs 2014), more mature and stable (v1.7 vs v0.x), has better tooling support (autocompletion in Visual Studio), is easier to install (you only need NPM), has better documentation, and is easier to Google (try searching for &quot;flow&quot; online!).  There are also plenty of common libraries with Typescript annotations, so you can just use e.g. Phaser and Typescript together without any extra work.  Other than that Flow and Typescript are fairly similar.  Perhaps someone who has used Flow can explain what makes it different from Typescript.