Poser 4 with Pro Pack is much simpler to use than P5. P5's new texture room is difficult for me to grasp and incomprehensible even with the manual. A lot of people have grooved on this new room, though, maybe I'm just slow. The new hair is a like a vampire that drains your system resources, I perfer the good old hair props of P4. I still haven't figured out dynamic cloth and the new clothing options. I've found the new P5 models somewhat limiting, but if you want to make Poser figures that look like friends and family there's the new face room where you can do that. If I had it to do over again I would have waited until more patches were out. If I were you I'd look at what both programs offer carefully and decide if you will really use the new P5 features, if not you might want to go with the simpler P4. One other note. The best thing about P5 is the Firefly rendering engine which produces much more realistic skin tones. That feature alone may make it worth your while to fully upgrade, however if you render in outside programs you might not.