Render quality is determined by how much processing time vs. power is applied to the image.  That power comes in many forms.  A powerful graphics card with CUDA can speed up a render a lot.  More cores/threads a CPU has can speed up a render.  If nothing else more time will result in a better render.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13