Stop by you're local large bookstore and look for a copy of "Maya Character Animaton-second edition" by Jae-Jin Choi(isbn: 0-7821-4328-8). If you have a lot of time you can browse through it at the store of if you're really committed you can buy it. It compares NURBS and subdiv modelling and thier uses (as the author sees it - all books are subjective). One of the interesting things that the author sometimes does is to model in nurbs patches then uses that model as reference to create a subdiv model. Although even the author the admits that he is increasingly modelling directly with subdiv.
For me personally, I prefer poly modelling then converting to subdiv when done an fine tuning the subdiv. But that's just me.