I've ran into several situations where our company has done a lot of proposal work and needed nice detailed renderings of vehicles with our products on it.  The easy part is finding a .3DS, .OBJ, ECT... of these models posted on websites.  If anyone has ever tried to translate these into SW knows about the nightmares of it.  So I'm going to search for a software where I can work with both.  Possibly getting these polygonal models and importing our SW files for constraining. 

So my question is what's a good software for that?  I've got a few in mind (rhino 3D or 3D Studio Max), but maybe somebody has some experience working with this.  I just need a somewhat easy to use program that I can work with both polygonal and nurbs surfaces.