I find that poser pro pack is the best so far. I used P6, and just couldn't see the use in the extra features, since i paint clothe and learning to paint hair. Soo... I went back to pro pack. However i agree, if you wanna get more realistic results try software like bryce or vue. I'm learning vue at the moment, slowly but surely.
I suggest if you cannot get shadows in poser correct and lighting correct, to correct it in photoshop. I tend to find no matter how bad my lighting in poser is, i can correct it in photoshop. However this is down to postwork skills.

 

Regarding your work, i think its excellent how you have a style of your own and please stick to it. BRAVO to you!

I believe your work can only get better with time and practise... keep at it!

 

Anna