I use both.  Originally a Poser user (since Poser 2) but lately I am using Daz more and more.

The main points for me are:

Poser (currently using 7) - I know this better so know how to get quicker results. The dynamic hair and cloth are very good (with practice) and about to get Poser Pro 12 for Christmas (mainly because Amazon had it for a mentally low price a couple of weeks ago on preorder, I snapped!)  I am looking forward to the new weight rigging and skin handling - I am told there is a lot of improvement on my aging version 7.  I also use Poser because it imports wonderfully to Vue 8, which I use a lot.

Studio (4 Advanced) - I am very new to this. I find it quicker to set up a figure/clothes than Poser but I haven't sussed the lights and shaders so not really getting the best renders yet.  The new Genesis figure is BRILLIANT, I am really impressed with it. Being able to fit clothes from a range of figures (and fit them quickly and well) is a massive boon.  It morphs quickly and easily and is particulary great if you do fantasy renders - making trolls and goblins is more fun than it should be.

 

Get the trials/free version and have a really good play. Their interfaces are very different, so find which you feel most at home with too.