the asgvis plugin is for Rhino 3 and 4, not 3d max. The plugin from Chaos Group is for Max.
I think Rhino handles imported geometry from other Cad packages better than max, but my max experience is a bit limited.
The max version of Vray has a lot more materials available for download though asgvis is working on a translator for the Rhino version to use max materials. The one that exists now only works if you already have Max.
The learning curve is a bit steep, but the results are really nice, and quicker than Maxwell. If you know other renderers, you shouldn’t have many problems.
Vray is a plugin for MAX. It’s build around GI (global illumination). The software is designed to be easy to use, and has it’s own textures and lights. It also has high-end features like blurred reflections and caustics. Some people find the lighting and materials creation in Vray quicker and more intuitive than in the standard MAX scanline renderer or Mental Ray.