Rendering speed in Poser depends on how you set up your scene. Poser6 defaults to render using the firefly rendering engine, which, while being very powerful (It is based on Renderman), it's power comes at the cost of speed, as it calculates lots of things that in some situations are not that necessary.
If you want speedier rendering speeds, you need to tweak firefly, or render with  the Poser4 engine.
Actually I do not use Daz Studio, but I do know for a fact that the poser4 engine is several times faster that firefly.
From what I have seen in the galleries, IMHO, for extreme realism, at least in Poser vs Daz Studio, from the results I have seen, Poser is the way to go.
But it really depends on the artist, and with what tools you feel confortable with, right?

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