@Frank_G:
Yeah you are right !
I didn't take account the time production side
If you want to go from a base mesh and just vary surface to make different characters : that's another solution.

Indeed when retopology you must keep a good polygons flow.
It's lot more easier to make low polygon by retopo than from scratch.

For Zbrush i found that :
decimation master plugin

It can be a solution to bring down the very high model or micro detail mesh to a high detail that can be loaded on your modeler where you will retopo.
For retopo you don't need at all the very detailled model !

Another soluton used by this great artist
Bishop tutorial
On Zbrush you can subdivide you model, and you can at any moment subdivide back.
So he just subdivide back the mesh to a lower resolution to be able to import it on a modeler.

Ok i stop for now
It was just me seraching how could i do retopo easily from Zbrush models (i think i'll do like iin Bishop tutorial).

But i persist
caus in 3D Coat , Voxel are vey different from Zbrush sudbivisons.

Voxel allow to really add or substract volumes lmike you want (pen, brushes, shapes ,objects etc ...)
You are lot more free, if you started with a base from, you can end with somehting totally different without having to come back


I know Zspheres 2 are a lot smiliar !

For the moment 3D Coat allow To do Retopo,UV and bake normal so easily and fast and with all in one :
I stay with it , sure.

For Zbrush, i'll have to study the best easy workflow i can find (i own Silo and Blender for Retopo and UV) !

Yeah 3D Coat rellay rocks a lot and for that prices, anyone doing next gen , can buy it , without any regret : it's a complete solution.

Not for incredible details and power of Zbrush , but you can already do something really detailled.
And for micro details if you really need them :
Zbrush has power to make them in polygons.
With 3D Coat : you can paint them on normal map !