Ok. I've been working on an animation for the last several months using mental ray. I've been really happy with the lighting results, but totally frustrated with the sampling. I switched over to unified sampling in mental ray hoping it would work faster...it did, but even with the noise in the image I was still getting 30min / frame @ 800px.
It was just too slow for an animation. So I thought I'd switch everything over to v-ray. WOW. Off the bat I was getting crazy fast rendering times with very comparable results.
I will say that the materials and lighting in mr are more "physically accurate", the results in v-ray are great considering the render times.
Here are my results...
If you want to know more about my sampling tests here are the links:
DMC vs. Unified