why include V4? and what do you want to measure?

realism is dependent on circumstances.  that is, if you do a scene that really needs glowing materials, caustics, colored shadows, high translucence, etc.  Poser is going to fail and so (mostly) is D|S.  on the other hand, i've seen photoreal renders out of Poser, D|S, Vue and Carrara. 

but then, i think if you really want to test realism, you need a control.  my suggestion is find a photo that's easy to duplicate.