I was involved in a similar testing of Vue6 vs 7 scene renders at another forum recently. Some points to consider:
- Only use "User Settings" for render settings. V7 has changed how it renders scenes in different base settings like Ultra-- so Ultra 6 vs Ultra 7 is no longer apples to apples.
- Make sure one is rendering the same scene on both V7 and V6.
- Make sure "optimize last render pass" is NOT checked in both scenes. Most people never use this, but one fellow did, and V7 doesn't honor this checkbox (except for Preview mode). I believe it's there for compatibility sake.
- Adding non-standard settings (like Systematic AA) is not a good way to benchmark render speeds in a global way.
I've found V7 renders substantially faster, and BETTER when using Radiosity vs V6. Most other scenes, it's a tad bit faster, but results are generally a bit sharper.