If you have Carrara 6 Pro you can Export the trees you make for use in Vue on close-up FG shots and use the ecos for the distant trees. You know in Carrara you can roll, rotate, or bend the leaves before applying them on the tree. This helps very much is the realism catagory as if done correctly the way Martin (Howie Farkes) does them in his images!!!

But on the Carrara note. Carrara is not very good at to distant renders, it tends to look a bit like Bryce, but Carrara is Fantastic for not to distant, close-up and indoor scenes. I rendered a scene indoors with Carrara that had the caustics of the Bigger Apps at it only took 18 minutes. I setup a scene in Vue as close as I could get it to the same and stopped the render after 5 hours, So Carrara's Indoor scene rendering is Fantastic, But I Still Prefer my Vue for most scenes!!!

I would rather be Politically Incorrect,
Then have Politically Correct-Incorrectness!!!