The advantage of a new head, as oposed to a new morph pack for V3 is that a completely different geometry allows for a dramatically different range of faces - that won't just look like modified versions of V3 (who tends to be instantly recognisable, whatever her morphs), the geometry also affects the range and style of the expressions. The advantage to making this for V3 is that she is free - so everyone is bound to have her. It would be difficult to conform this to another figue due to the eyes, it could be done but it would be a bit tricky. So far as I'm aware, the Poser 4 and 5/6 versions differ just in material set ups. There are some morphs with the base package but, like V3, you need to buy the add on for the full range. I haven't checked out the polycount but the obj is 4mb, which is about half the size of the whole of V3, so its going to be pretty dense.