I hope both programs continue to develop and progress for years to come, and both enjoy a sizeable userbase that will keep the companies that own them making a tidy profit.

Why?  Simple - competition is a good thing, a very good thing, for both programs.  Daz Studio does not yet have some of the features that poser does, but then again daz studio is a pretty young program in comparision.

Poser has more features overall, but in some instances the user interface can be clunky and some of the features (most notably the "face room") are so poorly implemented that they are nearly useless.   

As Daz Studio improves Poser must also improve to stay current and competitive, and vice versa.  Each time a new feature or a better interface is developed the opposing side must take notice, and do what they can to improve their own program to prevent it from becoming obsolete.

As to which is "better" at this point in time, it depends entirely on your application and experience.  For me, I've been working with Poser for a while now so I'm pretty familiar with it and as such it's fairly easy for me to do about 90% of what I want in poser relatively quickly.

If DS improves to the point where they have all the features that I want I might consider giving them a look - but for now it really isn't in the cards for me.  However your application and experience are probably much different than my own, so DS might be a better option for you personally.

Case in point, I have access to a full version of 3ds max, however I don't really use it all that often. Why?  Because I don't do much modelling and usually when I am working with a mesh it's normally only to make minor corrections.  As such I generally use a freebie program called wings 3d far more often than I do 3ds max.

Now 3ds max has features that Wings 3d couldn't even begin to duplicate, and it's a far more powerful program.  Comparing the two is like comparing a cap pistol to a nuclear weapon, they are just on two totally different scales as far as power and flexibility are concerned.

However for the most part all I need for most of what I do with meshes is a "cap pistol".  A simple edit here or there is generally all that I require, and as such Wings 3d does the job quite well.  I can accomplish things quickly because less features also mean a lot less menu options to be sifting through to find the one I need.

If I were modeling something complex, like a car or an airplane, I'd probably haul out 3ds max and use it instead - it has features that make such modelling far easier.  However for a quick edit here or there Wings 3d is more practical for my purposes.  

You might find such is the case as well with yourself and Daz Studio.  If what your doing is mostly rendering and you don't really need most of the features Poser has that DS does not, then DS might be a good option for you.  But really this is entirely in the eye of the beholder.  It will depend on your needs, your experience and your workflow.  

Just my 2 cents worth.