I last used Poser in 2002. Just last week I installed Poser Pro 2014 and started playing around with it again. Then I found an old hard drive in a box in the back of the closet from the computer I had back then. On that hard drive I found the install files for Victoria 2 (and essentials) and Michael 2 (and essentials). So I installed them, and guess what? They work fine in Poser Pro 2014. So for me, V4 would be an upgrade. But since I'm mostly interested in toon rendering (graphic novel style) V2 is just as good as V4 for my purposes, and probably as good as anything newer.

So I guess it really depends on what your artistic goals are.