M working on 3d smax 2010 from 2 months but its part time so i m not clear with the diff between mental ray n v ray as in my software i ve mental ray but no v ray so wats basically these both do to the rendering and wat is the dif thx
In theory there is not a huge difference until you start to push the rendering engines to their limits on large or complicated scenes.
Vray is a little easier to pick up and I find Mental Ray makes my workflow a little more awkward. This however is down to the individual. Overall they have similar controls and features.
I find MR images can often look quite gritty and full of depth whilst Vray achieves a smoother look. This doesn't mean that one can't simulate the look of the other but I do find these to be more their natural states.
There are a great many people who have asked this same question so I would suggest you have a look around at other posts and Vray/MR galleries for a more detailed understanding if you want.
In conclusion I would suggest that you give MR a go since you already have it to hand. Once you've got the hang of it try a Vray demo and then you will see for yourself the differences between the two. This is the surest way to answer your question, beyond the opinions of others.
3D animator and VFX specialist