Building an efficient mesh is an acquired skill in 3D modeling. A high resolution model may not necessarily be better, it may just have more polygons. Its a case of putting the detail where its required and being wary of the surface quad divide tool. Also NURBS modeling is notorious for creating high density meshes.
A good rule of thumb is to have a poly count comparable to a similar Poser model. For example the P4 male is about 19,000 with an OBJ file size of 2 Mb
Also remember that a lot may be accomplished in the texture.