WiMi5 vs FlatRedBall

WiMi5 integrates a powerful visual scripting solution based on Blackboxes that allows you to create the logic flow of the game. You don't have to code (if you don't want) but you can also do it. WiMi5's actions and behaviors resemble flowcharts where each box represents a function or value, with connections between them representing program flow. This provides a better at-a-glance indication of game logic than a simple list of events, and makes complex behaviors easier to accomplish.

WiMi5 provides integrated back-end services, with tools available to save game session data, manage rankings, etc.

The WiMi5 platform is free to use, supported by post-publication royalties.

WiMi5 provides features to manage in-app purchases and micropayments. Virtual Goods management is integrated into the Logic Editor.

WiMi5 maintains partnerships allowing simultaneous publication to a number of Web and mobile stores, all managed through the WiMi5 platform.

Games can also be downloaded and publish it wherever you want: in your own server or with your own partners. Just check the Download feature in the settings of your game.

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.