I think Flash CS4 its not fully supporting 3D, its just some cool functions, but its not a 3D engine. Papervision is more mature, so maybe we have to wait till CS5 to see this full 3D support. At the moment... CS4 have a good thing, IK Solvers, but in 3D, Papervision is still the king!
(shaders, physics, quads, modifiers...)