Vue handles atmospherics differently than TG2. Vue is more like Bryce on steriods, and handles the scene locally (as did Bryce). TG2 handles the scene globally. So on a macro scale, TG2 "should" have more realistic lighting and structure...its just a matter of learning how to bring this out.
I think Vue's strengths are its procedural vegetation system (I really hope TG2 has this one day), and there are some aspects of its renderer (GI effects) that I like, though its now not much better than TG2's, if at all.
Its kinda funny, but I spoke with one of the Vue rep's at Siggraph last year, and when he asked which app I used most, I told him TG2 and showed him some of the images I'd done in a portfolio I was carrying. He then stated something like "yea, the clouds and atmospherics in TG2 are far superior to Vue - but don't mention I said that."