I rendered the same scene using mental-ray and v-ray:
for each scene I applied different materials and lights, using the standard shaders (VRayMtl and mia_material_x) keeping the default options and changing just the necessary to render refraction, caustic and shadows.
My computer is a Dell Studio Xps 13, Intel Core 2 Duo P8600 (2,40 Ghz, 1.066 MHz, 3 MB), SDRAM DDR3, 4MB, with Windows Seven.
 V-Ray Shaders: VRayMtl Render time: 5:22 sec |
 Mental-Ray Shaders: mia_material_x Render time: 1:12 sec |
I prefer the V-Ray render, the quality of the refractions and caustics is much better, but the render time increases a lot!
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Feel free to change attributes and try new renders. If you download it, feedback is welcome, thanks! 🙂