I am not really great at 3d, but
I have been using Wings3d for a while, and
it is amazing. People say that the workflow
is quicker than most (some people prefer certain
modeling over the expensive modeling because they
can do everything quick).

Blender can do a lot more, though, so maybe start out
with Wings (much easier to use), and then switch to Blender.
Blender has radiosity baking, polygon reduction, a tree generator
(seperate), FBX level export, and more.

Truespace I don't know much about, but Blender is constantly
imporoving without a charge (so in the long run, Blender
might be a better bet).

I am not a professional, but hopefully what I said could help.

-Jim