As has been stated, both Bryce and Vue have benifits and drawbacks. This is a list of my opinions based upon my very limited experience with both;

Vue Pros:
More varied vegitation (small in absolute number, but you get flowers, ferns, shrubs, trees...all randomly generated to be different from others of the same type)
Standard user interface for 3D aps
Faster render time
Three user defined cloud planes available within the sky dialog and user defined altitudes for each
Simple Poser file import (including animations with Mover addon)
Planets and moons available for placement in sky settings
Inherent lens flare (if you desire that sort of thing)
$199 base price

Vue Cons:
Stardard res renders are grainy
Though varied, indivdual plants are not easily manipulated
Has a history of being "buggy"

Bryce 5 Pros:
Deep texture editor (though difficult to master, the results are worth the effort)
Treelab allows for virtually unlimited creation of trees
Metaballs
Terrain editor is far superior to Vue
Image quality is superior at lower settings then Vue (you get what you wait for)

Bryce Cons:
Non-standard interface (easy to use after working with it for a while but daunting for nubees)
Poser imports require a good deal of manipulation
Slow render (again; you get what you wait for)
Two random cloud plains available in sky lab and both are at the same altitude
Sun and moon cannot appear in the same scene
Tree lab can ONLY make trees. ALL other vegitation must be imported
~$150 more base price then VUE

I am currently using both programs. I like Bryce for interior and other shots that require little vegitation. I like Vue for the scenes with lots of vegitation. That is the deciding factor for me at this point. Hopefully Corel will expand the "Treelab" into a "Plantlab".

The Mover addon for Vue would be a major factor for anyone wanting to animate Poser files. Adding Mover to the package brings the price to just above that of Bryce, but the results are amazing.

All other differences between the programs really can be worked around.