I have used both extensively and I believe VRAY is a phenomenal renderer for quick and easy turnaround jobs like TVC’s and print work etc. MR is phenomenal for longform work and Movies, where you have time to tweak and tweak and tweak every little setting.
One of the biggest problems out there for MR is that because it is so complex, and there is no “render beautiful image” button, alot of newbies give up on it as there isnt really alot of dumbed down learning resources on the topic. That is why it is used so much in movies because they have the time sqeeze every little once out the renderer and they have seasoned professionals working with it. But remember it can do everything VRAY can do and a whole lot more, you’ve just got to know what you are doing, as Jozvex demonstrated with those images. Also dont forget the power of rendering in passes. Its amazing how fast MR can get when you split up your renders into an ambient occlusion (oh how i love theee), key light, rim light, shadow, reflection etc…
Vray on the other hand is sooooo user friendly in that you can setup a few options and there you have an amazingly beautiful image with relatively quick render times. But it isnt as deep as MR is. Plus VRAY isnt for Maya (YET…OMG HURRY THE F*#$ up) so it isnt as widely used.
Its going to be very interesting when VRAY,Final Render and Brazil come out for Maya. As all are in the making at the moment, if they have the same speed and ease of use that they have Max, then i think MR will be in a bit of trouble, simlpy because they are such great renderers.
Turtle is nice too, very speeeedy. Havent used it a whole, lot though just yet.