I have some experience with Vue5e, Max 6 (as Viz2006) and with the Carrara5 Pro trial version. No experience with Maya.
Of your available choices I would go for the Carrara because it is stable and has an excellent texturing, assembling and rendering function. I have found both Vue and Max to be disappointingly unstable - crashes - even for the pros. If you are going to build scenes, Carrara seems second to Max-except that Max crashes so often. Max is very unforgiving of "wrong" inputs. If you know Poser6, then you know something, at least, about Carrara user interface as they are a bit similar in important ways. Rendering in Carrara (which would include very advanced textures, shaders, lights and so forth) is far advanced to many other software except maybe the very highest end. If you decide on Vue5, do get 5Infinite because the lights in Infinite only support accurate shadows which are an absolute must for good rendering. I also use Cinema 4D and in some important ways, Carrara seems comparable - not all ways - but some very important ones - especially if you don't want to model in Carrara. (Hex, Modo and Cinema are superior modelers)
You mention that you will assemble in Poser - much easier in Carrara. You also mention that you will render some scenes outdoors - infinitely better in Carrara.
Maya? Don't know - download the trials as suggested above. I also know that you would want to think about the community that supports your learning curve - ie: forums and tech support. Carrara seems very good to me so far - I asked a question on the official Vue forum at Eon over 10 days ago and no answer yet. I've ordered Carrara5 Pro. I want in on an affordable upgrade path and a good renderer/scene builder/atmospherec modeler. If cost is no object whatsoever, but reliability is; I'd look at Maya and then decide between Carrara and whatever you find out about Maya. This is a great forum here and at the Eovia site as well.
Regards, wb

Message edited on: 01/13/2006 19:39