FlatRedBall vs Blacksmith 2D

Just check the commit frequency on github :)
https://github.com/vchelaru/FlatRedBall/commits/master

Plus Victor takes community input seriously and is known to shift around priorities based on the pressing needs of the community

Simplifies routine tasks such as adding entities and files to the game, or tuning parameters, via the FRB Editor called Glue

Very active chat on gitter: https://gitter.im/vchelaru/FlatRedBall
Victor (the creator of the engine) is available throughout the day to answer questions and solve any problems that may arise, along with the rest of the community members who are ready to assist in any way they can.

http://flatredball.com/documentation/
Very good documentation not only regarding the API details, but also lots of tutorials covering different aspects of using FRB, either on the code-side or on using any of its tools.

Automatically detects changes and updates bitmap cache. Allows to gain even more performance on heavy scenes and runs smoothly on old devices.

All engine code is written in ES6, fully GCC typed, allowing to eliminate all dead code from your app.

Dirty flag tracks scene changes and avoids unnecessary calculations and context calls. If no changes were made to the scene since last frame, no rendering will be done. Battery efficient.

According to the tests on the Github page, the performance is better than in Phaser!

The source code is well commented and easy to understand.

Super small build size through dead code elimination. The best for playable ads and Facebook Instant Games.