I have both and like both of them for different needs, For example Vue has better plant generation for the eco system each instance is a new gen of the base plant so each instance is unique.

Carrara has more control for placement and some options to change random scale and size as well as rotation of the object but its still a copy of the origonal object.

I am using Carrara more and more, Vue is a great package but way to many patches and still problems (I still cant export a plant object properly) I use Vue mostly to make .hdr for Carrara.

You dont need Carrara 5 Pro as Standard will do what you need.