While Caligari True Space looks cool - as far as the ads showing it's capability, I've never seen it in use, never seen any tutorials for it - heck I've never heard of it being used in any professional known product (game or other). Bryce is a fairly cool terrain mapping program, but I've only dabbled with it, though have seen more use of it by the industry. Anna Meyers, a member here uses Bryce for her Greyhawk Maps.
I've used Raydream Studio, a rather old, low-end 3D app, as well as Nendo, my favorite subdivisional surface modeler, and Cinema 4D - a higher end 3D app. Really you should be looking at an affordable version of Maya, or the industry standard 3D Studio Max - the latter seems to have more classes available, so is more of an industry standard.
3D tools like graphics tools are up to personal choice by the artist using it. It's difficult to judge which would work best for you. Download demos and experiment would be my best suggestion.