I have done extensive modeling in Carrara.  The spline modeler is a nurbs modeler but it has limits.  It's not a full blown 3d spatial nurbs modeler.

For vertex modeling, hex is probably a better bet.  It's a little more of a learning curve than C but it will do a nice job.  There are a few extra very nice tools in Hex over C.

While C can do a lot of modeling with some patience and knowledge, as just a straight up modeler, I would opt for Hex first.

Vue can render some things better than C and C can render some things better than Vue.  In their respective specialties, they both can bash out great results.  However, if you've already laid out the coin for Vue, it will probably serve a lot of your needs.

While I am a hardcore C enthusiast, I would not recommend C unless you are rendering something that Vue struggles with.

-Kix