Please correct me if I'm wrong but it looks to me as though you have the captions reversed. The hard edged cube is what I'd expect from RDS while the cube with the softer edges is what I'd normally see it Poser. As to your problem, getting Poser to render a hard edge isn't an easy task. It's set up to soften edges like you'd expect of an organic form. My experience has been that if you add a lot of polygons along the edges, the crisp the edges will end up when you render the model. There is a tesselate function in the MFM that should help with that.