Going to use Shiva3D for production:
The license is cheep 200$;
No royalty's requested;
Offers a server for multi player with high quality;
LUA scripting language;
Pure C++ development on the engine;
Most cross platform engine;
Width range of tools set to work with;
Web 3D player;
Linux support;
Publish to most if not all mobile devices;
Is not very known but the company is around from 2005;
They are writing their new version of software 2.0 which will improve all features, which will make it a very stable engine;
Other options considered and discarded:
Unity: expensive to purchase license 1500$, not that great support for multi player, free version don't support graphics quality so is kind useless for commercial development.
UDK: no extensive support for multi player, royalty based, although high graphic quality the low support for multi player a major draw back.
Cry engine: no commercial development unless paid high values.
Hero: major draw back only supports 30% royalty, but high quality engine;
XNA: although looks great, and is been around for a good time since 2004, the lack of support not what to make one jump in to it. Low platform compatibility;
These was the information that I was able to gather post your thought but don't inflame is not a debate on what is best, just a mater of excluding possibility's based on project objectives and personal.
ps: found a couple of links that explore the potentials of the engine:
http://www.youtube.com/watch?v=e_HhOp-NWNk