Carrara renders are usually sharper than Vue one (actually Carrara and TG2 render have often similar sharpness and luminosity) while Vue ones are often softer and somewhat darker.
If you have a look at this DAZ product
http://www.daz3d.com/i/3d-models/carrara-add-ons/stoney-creek-beechdale?item=9370&cat=262&_m=d (from the same HowieFarkes), you will see a render which has nothing to envy w.r.t. to Vue foggy/dreamy ones.
The most interesting aspects to all this are that:
1) Carrara costs a lot less than Vue and is an all-inclusive modeling/rendering application;
2) you can get most of Carrara experience just using the standard version;
3) HowieFarkes sells on DAZ his scenes, so you can get them and tear them apart, learning his techniques.
Bye!!!
P.S.: just a note, calico: those trees are not external XFrog meshes, but Carrara trees... Carrara tree engine is the most powerful I have ever seen outside specialized botanical applications.