Um, Carrara 6 allows you to open Poser content just as easily (if not more so( as Poser.  A lot of folks have switched completely from using Poser to model and pose characters then render in Carrara, to doing it all in Carrara, I haven't touched Poser in over a year.

Quote - They both are very slow renderers.  Vue specializes in terrains and vegetation.  Carrara generalizes in modeling, texturing, animation, and rendering scenes for film and/or illustration.

For content purposes, Vue imports Poser while Carrara imports DAZ.

Both are version 6.  Both have version 7's being worked on that don't add much new stuff.