Selected quotes from V5I manual (p135):

Broadcast: this render setting was introduced for animation purposes. (This section goes on to explain about improved AA for rendering motion blur in animations...)

Superior:this render setting is similar to Broadcast, with adjustments made to improve quality .... and is significantly slower than in Broadcast...

Ultra: this is the best render quality available. It is also not very useful, since it takes several times longer to render than other setting, while not necessarily producing outstandingly better results. Use it only when you want to render very high quality pictures, for publishing.

Since I don't publish and don't do animations, I never use anything above Final:-))

Also, I don't bother with Vue's booleans. I find it quicker and easier to use a 3D modeller to create stuff (and it usually results in a lot cleaner mesh)...

Cheers,
Diolma