You're right, I find out that SH3D and wings3d generate different normal directions: while in SH3D vertex normals are orthogonal to faces, in wings3d they spread out radially;
Also the amount of normals and faces is different.
This affercts somehow surface reflection and material refraction.
I tried to export form wings3d to 3DS and then import in SH3D but unfortunately the resutl is quite the same.
So I think there's no way to solve the problem if I want to keep on modelling in wings3d
