Poser Series

The Poser series are another type of rendering software, geared more for the advanced user.  They offer you more options for your rendering, plus a more robust graphical rendering software. 

Poser can do all the same as the afore mentioned DAZ3D plus gives more options for animation and more lighting and shading options.  It supports a more robust software to allow you to be more complex with your renders and have to rely less on post work.

Unfortunately, unlike DAZ3D studio, Poser is not free.  While the program is excellent, its price tag can make it somewhat restrictive.

Simply put, it is the more advanced of the two.  There is no major difference in results, and in mostly come down to personal preferece.