Poser 5 has a much steeper learning curve than Poser 4. If you're a quick study, or already experienced with 3D software I'd say go straight for Poser 5. It has its faults, but so does P4, and you can do so much more in Poser 5. On the other hand, if you're someone who struggles to learn a new piece of software (as I am), start with Poser 4. It's easy to learn, there's oddles of free stuff available for the Poser 4 figures, and you'll be able to concentrate on being creative rather than struggling to learn the technical stuff. Then upgrade to Poser 5 or Pro Pack when you're a confident P4 user. You'll be in a better position to make an informed choice between them by then (and depending on how long you wait, Poser 6 may be another option to consider, too.) BTW, I have 256 RAM on my PC and Poser 5 runs happily. I do occasionally get crashes, but no more frequently than others report, and none since I installed SR4.