FlatRedBall vs ShiVa

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.

The free ShiVa Web version is limited to web publication, but otherwise has the same capabilities as the $200 ShiVa Basic. Upgrading to the $1000 ShiVa Advanced brings tools geared toward team development and professional releases, such as integrated SVN support and profiling tools. All versions are royalty-free.

All game logic can be scripted in Lua. ShiVa also provides a cross-compiler from Lua to C++, allowing Lua scripts to be further optimized and compiled to native code for performance.

In addition to the help forum, Basic and Advanced licensees have chat and direct email access to the developers.

Smaller platform specific executables, native code export, good FPS even for complex scenes. ShiVa has great advanced optimization features, including PVS and LOD, decreasing number of drawcalls even in complex level. Platform specific profiles allow developers to customize size and compression level for textures and test those settings directly in editor. Other engine features, like lightning baking, mesh combining and GPU skinning will boost performance too.