I use the DAZ figures over the default Poser figures for several reasons:

1. The DAZ figures are more realistic-looking than the Poser figures
2. The DAZ figures have more built-in morphs/morph add-ons than the Poser figures
3. There is more development that goes into the DAZ figures which makes them more versatile than the Poser figures
4. There is a better track history of improvements from generation to generation of the DAZ figures than the Poser figures (Brand recognition: Michael & Victoria have some standard of quality associated with them)
5. The DAZ figures have more content available for them than the Poser figures
6. The DAZ figures bend and pose better than the Poser figures
7. With the exception of a few figures like Apollo Maximus and Antonia, the DAZ figures have very little competition in terms of realism, especially not from the Poser figures
8. The Poser figures have been tied to additional capabilities such as Face Room which can give decent results, but only with a lot of effort.  Very few people want to go through the effort when the default figure is so ugly (unhuman looking) to start with.

Personally, I think that if it's desired for the Poser figures to be more aesthetic and user friendly, perhaps SM should consider contracting out to Zygote as the source for their human models.  Which would be ironic considering that DAZ originated from Zygote.