Ron,
The thing about Carrara is you really have to work on the modeling (I tend to stick with vertex, there are more advanced options but they're a bit beyond me, and vertex has some nice tools) but that's OK. You tend to appreciate the physicality of the things you're modeling, it's not just mathematical expressions. Once you get a hang of the modeling, the lighting and texturing options surface as the program's strengths. The artistic potential is as important as the accuracy of the virtual engineering.
I've tried a few similar 3D programs, but I guess we stick with what we start with.
Mike