DOF ?! well when I use this feature then probably in a Photo application making more sense, better choice then you can also postwork your render for preference :) Resuls in poser are not accurate enough when getting at this point. In the case of your Render it is changing with using  DOF a Story from a skater in a skating room into a simple Pinup render. But it is individual what the creator wants to present, either a Skater in action or just a pretty pinup .... So blurring out the background allot of times has the effect of erasing it and with it the story. I like the First render without blur as this one is telling a story :) The other one is just a pinup like seen allot of times ( Darn where'd I put my glasses ) Sure if you want to sell an outfit  then the second blurry one is the better choice ....