But also don't mind pro/e and solid edge. The difference between rhino3d and the others listed is the others are parametric, basically a history based part creation. Parametric is good for real product manufacturing as it allows for easy changes to one part that effects everything that part is constrained to. But the reason i like rhino3d as it is easy to use, fun, and very fast to create a part. I called this type of software free-form modeling as you are free to do what you want when you want it, i would group programs like maya and 3dsmax into this also in terms of how they modeling objects.