Personally never owned p4. Played with it on a work computer a while ago (before p5 was out) and didnt care for it. It felt too limited, especially in the texturing,rendering and the lighting aspect (I'm used to maya's node based texturing). The lighting in p5 still needs a lot of work, but the other aspects have improved hugely. Yes it initially had it's problems, but all things factored in, it's a pretty decent package now. Especially considering the price compared to other 3d "character solutions"