Dont know why, but theres only a trial for the version 6.1:

http://www.daz3d.com/i/support/downloads?product=car_down&_m=d

Carrara have a lot of tools from Poser and Bryce. At same time it cant do a lot of things that Bryce or Vue can easy, but you can do a lot of things with it without need Bryce or Vue.
The main goal for Carrara is that you can build your own content and control many things inside it in the mesh (because you cna model, texture and rig in it).
You can export OBJ files from any software to use in Carrara too. I thinki the trial version can answer better your questions.

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