IMHO the major factors regarding which you product you use can be over simplified to two things.

1. What "feels" right - a workflow and tools set that most closely fit with the way you think.
2. What product has the best tools for what you want to do - even if you like DS better - if you need to make and use your own dynamic clothing, you would need to use Poser

I use both, but tend to use Carrara the most, then DS3A, then Poser (also use Hex, and sometimes and old copy of C4D). Poser Pro2010 has improved a great deal, and I was finally able to get a render I honestly felt was pretty decent out of it (something I wasn't able to do with previous versions). But it did take a lot more work than DS3A or Carrara, simply because I've never been able to wrap my head around Poser lighting.
Example Image from Poser Pro 2010 here:
http://www.renderosity.com/mod/gallery/index.php?image_id=2036580

With DS3A I was able to make some decent images with good lighting fairly quickly. 
The light setup on the next link was done with my first attempt using the included UE2, with less than 15 mins. of light setup time (VERY fast for me).
http://www.renderosity.com/mod/gallery/index.php?image_id=1994089

Carrara is what I use the most, because it is what I know the best. I feel comfortable with Carrara, and understand lighting much better than with DS or Poser. The next link is to a Carrara image.
http://www.renderosity.com/mod/gallery/index.php?image_id=2023770

If your feeling limited by DS, you should give Carrara a try. You can get Carrara 7 Pro for free with Issue #17 of 3D Artist Magazine (see discussion here; :http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2804832).

Bottom line - I think that the choice of what program you use is largely determined by how well it fits your own logic. Many Poser users find the DS interface too difficult and confusing. Many DS users say the same thing about Poser. Of course many Poser and DS users also say the same thing about Carrara.

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