What are you planning on doing with the software where you want import Poser stuff into? If we know your goals, we can much better answer your questions......

Is it for landscapes only? You may want to with Vue OR consider doing landscapes in Poser itself, by using MicroCosm 2.0 & Terraformer and such with a number of trees and plants for Poser with it for example.

Is it to have a better rendering engine or to render larger scenes? The both Vue and Carrara will work.

Do you want to create landscapes, but also model let's say you own cars and houses for example? Skip Vue and go with Carrara.

It depends on what you're going to do with the software that determines what is the best.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk