"The Material Room is worth getting to know in P5. It will make a critical difference in the look of your images if you take the time to get to know what's going on in there." Um, this isn't optional. Unless you use only pre-made MAT poses you will HAVE to learn the P5 Materials Room. On the rest, I agree; you can skip hair, dynamic cloth, and the content parasite, use just render presets and the thing becomes pretty much P4 with a different-shaped window (and better renders). The dynamic cloth, tho, is also "worth getting to know." It is very confusing at first and the manual is no great help. Go with Dr. Geep's tutes instead. But once you figure out how the cloth room is organized you'll get quickly used to it -- and you'll find yourself reaching for dynamic cloth on every image. From my perspective, the major learning hurdle in P5 is a lack of consistent GUI standards. Different rooms have striking differences in metaphor and layout, and different pop-up windows have different behaviors as well. It isn't as smoothly integrated as the main work area in P4. Other than that, the core concepts you need to learn are about the same for both programs. If you are starting from scratch, neither is remarkably easier or more difficult than the other.