If you want to do terrains and the like; there is no better solution than Vue in my opinion.  Vue does import Shade objects; so no worries there.  I have both Shade and Vue Infinite.  If I am wanting to create a scene using landscapes I use Vue.  If it is an interior scene I will use Shade. 

I find it easier to use Shade if all i am doing is rendering a standard Poser scene without adding other items.  I believe the renderer is better for that type of scene than Vue's.  However, with 6 coming out next month that may change.  I will certainly get the upgrade myself.

I do have to add that Vue does extremely well importing Poser figures also; and with version 6, promises to add even better Poser integration.  As it is now in 5; it's very good.  With 6, I expect it to be fantastic.

My overall suggestion?  Get Vue.  It will be easier to learn, and will give you more options.  Take a look at the gallery here.  There are some really good examples.  (Mine not included; mine are very poor)