Hi Spartacus,
So you want the egg shell to break and open, right?
I suggest that you model every peace of the shell. To do so, you can first model the whole egg, then cut pieces into it. This way you pieces will remain seamless. If they are not seamless, what you can do is make a copy of your original egg (not cutted), cut pieces in the original, scale just slightly the copy, and make it fade out when the cracks are to become visible.
I think that polygon objects is more suited to this. If you use nurbs, you'll have to make the piece's edges look rough with textures.
As for the animation, well I don't think it's big challenge to make piece drop on the floor. But of course you can use dynamics..... But personally I wouldn't go with solution. The complexity of the animation does not worth the amount of fine tuning.
Hope this helps!
Bernard Lebel