They're been numerous of threads on this topic and all of them with the same result, go for P6. Poser 6 is Poser 5 with all of the needed improvements, great rendering and feature additions and a number of good (imo) new figures and some excellent new content.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk