What I didn't see mentioned but may have missed it.

If you do not have the morphs++ for M4 or V4, you have less than 20% of the usefulness of the figure.  Adding these makes them much more versatile  And, Nerd has a free download of weight mapping for V4 that is another boost to the figure, it works magnifcently.

If you have an investment in dynamic clothing for Poser, it will not work in DS, any version.  DS also does not support dynamic hair, any version. and DS dynamics will not work in poser.  Weight mapping for Poser, I don't believe works in DS.

If you have P8, there are upgrade paths to 2012 or P9, although the bite is still healthy.  It is no worse than the bite would be to go from there to DS4 and Genesis based figures. 

My advice, the morphs++ would probably make the best investment then see if you want to move to something else.  What you need, not what someone else says you need.

The "I" in Doric is Silent.