Very interestings comments in this thread.

Since a couple of days I am wondering about a new 3D tool for my project.
I thought to work with Shiva, but my first feeling is ambyvalent and I did not like my first experiment with terrain editor. (sorry Broozar )
So, I have downloaded C4 demo, nice looking features but getting jammed in every demo I have tried is irritating.
Then I have downloaded NeoAxis demo. In this demo, graphism is poor but I do like the technical part !
Today, I will try Irrlicht (because I trust Machinery_Frank )

Then comes the price question:
Shiva is free to try, yes, but at the end it will cost at least 199 € and much more if you need LOD !
C4 is at a good price today, 200$ with unlimited updates , but this offer will end soon.
NeoAxis for 99$, with free upgrades to V 1.0 might be a good bet.
Irrlicht ?