Don't forget Vray for Maya, Vray for C4D, Vray for Blender, etc. All the same interpolation based algorithms. Also Vray for Max came first, so it's had longer for the kinks to be worked out. As a platform, Max itself has many advantages over SU with polycount and it's quad modeling nature (and turbo smooth technique) usually resulting in a cleaner mesh. The way the mesh is processed is definitely reflected in the rendered results. Max also has far better RAM management, as it's scenes are constructed in a referenced format. Textures are not stored with the Max scene, but loaded dynamically from the hard drive. Also the modifier stack in Max is such that on the base of the stack is stored with the file and the modifiers are also dynamically loaded into the viewport and calculated as the render is taking place. Proxies are another thing that are referenced from the hard drive and only dynamically loaded while rendering. All that being said, for the novice user, I think it is easier to get a clean result out of simple scene with VfSU as the sun and camera are derived from the SU viewport, whereas the user in Max needs to know how to set those up for the best results. I've also seen a ton of renders done by some Vray masters on this forum that rival and surpass a lot of stuff produced by Max users. It's all about maximizing the tools at your disposal and knowing how to be adaptive to different scene conditions.
It's actually quite surprising to me that Vray is still the "king of the hill", even as computer technology has grown to the point that unbiased solutions are almost as fast as biased solutions. I think in the future, unbiased will win out......when realtime speed and accuracy are one in the same.