The faces and expressions are naturally much different in a 3D world where you build a model of a face once and then animate it, as compared to the 2D world where you repeatedly paint the head in different positions and moods.

This file contains two videos, in the first a face rendered with subsurface scattering in an effort to create believable skin, in the second the face goes through a series of expressions.

However, the videos also show how many things you have to take into account when dealing with 3D animation. The eyes and teeth of the model got a very strange and shiny surface by default, and we didn't correct it as it was immaterial to the test. Also the second video has a very early and not very good hair system applied.