I havent read the whole discussion, but if I may, I will give some tips when Im looking for a game-engine:
1: Flexibillity: Can it make all sorts of gametypes?
2. Licence: Commersial, source and price
3: Community: How friendly and active is it?
4: Updates: Is there regular updates?
5: What can the engine do? Level-editing, lights, vfx, audio, systems like weather, water and time-of-day and material-editing. I also look at importing-options.
Unreal Engine meets my needs and I will stick to it as I enjoy the community and how the staff takes care of us and the engine.
Thanks 