Between Maya version 5 and 7, Alias added a lot of powerful features to the Maya commandline renderer. However, these features also complicated the lives of render managers by completely changing the interface to the program. Originally, you could only use the Maya software renderer, so the product “Maya” originally referred to that. The “Maya (1-5)” product still works in this manner
With Maya 6, Alias added the ability to select a renderer from the commandline, and made 4 renderers available: Maya Software renderer, Maya Hardware renderer, Maya Vector renderer, and mental ray for Maya. In response, we added “Maya Hardware”, “Maya Vector” and “MentalRay for Maya” Products to Smedge, but still used the “Maya” product for the default behavior of using the Maya Software renderer to render your scene.
Then, Maya 7 added a whole new wrinkle with Render Layers. Render Layers now allow you to use a different renderer for different layers inside the same scene. In order to handle this properly, we changed the Smedge Products to match. Now, the “Maya” Product tells Maya to use the renderers that are specified in the scene file. The “Maya Software” Product will tell Maya to override the Render Globals or Render Layers renderer and force the use of the Maya Software renderer.
If you are using Maya 7 or later, we recommend using the Maya product. This will give you control over the renderer at the scene level. If you are using Maya 6.x, then you should use the appropriate Maya renderer override product (“Maya Software”, “MentalRay for Maya”, etc…).
Note: When using the "Maya" Product, Maya does not allow you to override many of the features of the renderer. You can override some basics, like the rendered image filenames and output format, size, and a few others. However, you cannot override most other parameters of the renderer, because Maya does not know which renderer will be used until the scene is loaded, and each renderer has its own command line interface for such modifications.
The most important side effect of this is that for any renderers other than mental ray, you cannot override the number of CPUs that will be used by the renderer. The renderer will use the value in your Maya scene's render globals for each render layer. Using the Smedge CPU settings (e.g. "One per Engine" or "One per CPU") will not change how many CPUs are actually used by the renderer, and only affects how many work units Smedge will allow to start on a machine. Be sure to set the value in your render globals to a value appropriate for the machines that you will be using for your rendering, or use one of the renderer-specific Maya Products for your Smedge Jobs, like "mental ray for Maya" or "Maya Software Renderer".