I need a 3d program with a viewport (that can view a textured sphere mesh) and that I can place vertices onto the sphere's surface using the viewport by simply dropping a vertice onto the sphere's surface found in the viewport. Thus, each vertice lands exactly on the surface of the sphere. So, i don't need to precisely position each vertice accordingly. Rather, each vertice that i spawn in the viewport will land exactly on the apprioate mesh surface.

If you want the most versitile 3d program, used by almost all of the big companies, go for Avid Softimage, it's my modelling program of choice...

Although no program really accomplish placing at vertice on the plane from the view point standard i find that softimage/xsi makes it easier than maya or max...

3DS Max --> Editable Mesh --> Polygon/Face mode --> Divide --> Click where you want the vertex.

or 3dmax edit poly mode, edge select mode, insert vertex.

And moved.

How about Lightwave, here is an example that shows a head in the making. The tools used are mainly drag, mirror half, kill half, bandsaw, smooth shift and edgetool.

Example (http://homepage.ntlworld.com/scitzo/edgetool.zip)