I have been using Maxwell for Rhino, although it is super slow but it gives me the best result compared to Vray.
Simply because Vray version for rhino is outdated (2.0) if you compare it to 3ds max or maya, Vray for Rhino is no match. that is why I chose maxwell.
it takes a while to get the good setting for maxwell and it is faster to learn compared to Vray (took me 5 years to get a hang on Vray for 3dsmax and only took me less than a year to get a hang on maxwell).
also, if you are an architect, all maxwell unit are in SI, that means your lighting setting will be physically correct and u can use that for lighting study for your interior scene. and multlight feature in maxwell is the thing that is very useful for designers.
the only disadvantage of using maxwell is because it is CPU-based at the moment ( soon they will release GPU-based) that is why it is so slow if you dont invest your comp with enough memory.
the other thing I want to mention is the noise problem, there are some photography techniques to reduce the noise, and it depends on how you light your scene. most maxwell beginner complains about the noise problem because they just expect to get a good clean render by simply hit the render button.
I like both Vray and Maxwell. however I wouldnt recommend using Vray for Rhino, if you want to master your Vray, export the model to 3dsmax to get the best from Vray.
if you want to stick doing rendering in rhino, maxwell so far is the best choice if you are looking for high quality (photorealistic) rendering
if you just want to do a concept rendering then there are many other renderer that can offer a fast and “okay” result.
Maxwell works best for product rendering as it can produce accurate DOF, real world caustic and specularity. not to mention all the settings are in SI that means u can get all the IOR, or other luminance setting info directly from google or Wikipedia.
yes it is a big issue that there is no direct integrity between rhino and maxwell, because maxwell works as standalone rendering engine. you will have hard time at first trying to adjust rhino camera and maxwell camera, and sometimes if you accidentally create a bad object in rhino, it will crash during voxelisation.
so I would recommend you to go back to maxwell, that is the best rendering engine for rhino,
I was hoping one day rendermanPixar would somehow be implemented in rhino, but that is just a dream as for now :))
sorry for my weird english