A subtle point here... There is no such thing as Poser 4 anymore. The new name is Poser Artist, which is basicly the same product in a new box. The Poser 5 features that I really appreciate are: The Material Room, the Cloth room and the possibility to organise your library better. The last one is not to be underestimated. Your library will quickly overflow with products and freebies, and Poser 4 only allows one folder level... These three features are reason enough to go for Poser 5, in my opinion.