I've seen some cool stuff done in Poser with the right combination of shaders and lighting.  Just like any renderer, it requires some work to hit that sweet spot.

That said, I'm a Vray user on the 3dsmax platform.  I find Vray has the best marriage of speed vs. quality of any render agent I've tried so far, including MentalRay.  The downside is, there is no Vray integration to Poser that I'm aware of, and although it's available in one form or another for Cinema4D, Maya, Rhino, and a few others, the most mature version of it is for the 3dsmax software.  After all, it was originally developed for 3dsmax specifically.

As far as standalone renderers, there are a few good ones out there.  POVray can assist in creating some amazing art, and Maxwell has one of the most realistic, although slowest, lighting solutions available.

For more of a hobbyist budget though, I would look at Vue or Carrara.  Very good renderers integrated into those packages.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.