There is a little difference for 3D Coat: you can modelize entierely from "Voxel" (microscopic cubes)
and at the end transform in classical OBJ polygonal format.

ZBrush has not this function (only hidden for the user for few functions (Unify Skin, ShadowBox...)
And modelise by ZBrush "Shadow Box" Plane by Plane is not the same than 3dCoat
Another difference : 3D Coat has a classical Interface! ;)