Carrara 5 Pro  has the surface replicator feature which is similar to Vues Ecosystems.  Carrara can replicate 1000's of tree instances which is something I miss in C4D, I am quite sure Carrara express doesnt include the Surface Replicator.   I would go for Carrara 5 Pro from the 3D world magazine, it is a full featured 3d app which is fairly strong in the landscape area.

Mike