You can ignore everything CobraEye says. He never has a clue of what he's talking about. In a recent post in another thread it became obvious to everyone that he's probably still using Vue 4, as he didn't even know about a feature that was introduced in Vue 5. That tells a lot about the value of his posts.

Vue 7 is faster than Vue 6 for comparable render quality, for most of the environments or situations. Of course, if you compare Vue 7 render time in spectral2 clouds with Vue 6 render time in spectral1 clouds, then Vue 6 is faster because spectral2 clouds are slow to render. For example, one thing where Vue7 is much, much better is in handling displacement. With Vue 7.5, all the CPU cores are used to handle procedural terrains, dynamically populating ecosystems, etc, unlike previous versions. That's a huge step up.

There were a lot of posts by chippwalters and others about render time comparison when Vue7 first came out, do a search and you'll see.