There is also few problem like the like of global illumination or lightbaking. But as far I know I never experimented so much ease in game developpement.
Theses are some experiments. I'll try to create such environment in the UDK.
I did pick the cryEngine at the beginning because I was trying to create a dense forest for my game. The first part is set in a forest and the main character is pursed by enemy and unarmed.
So the cry engine was the best choice for my game. I even gave up the idea of selling this game in order to get a powerful engine ( tired to create my own tool) but the UDK came so I'm trying to port everything I had so far and learn how to do realistic outdoor.