Maya have one of the greatest features around, render layer overrides. This is letting you make different settings all over the scene for only that render layer.

Ex. You have set up the first render layer as the master beauty. It is using ray tracing because you have mirror reflectivity for some materials. For the second render layer you only want to render the lighting from one of the lamps with a buffer shadow. You set up a material override and a light group override. But you cannot turn of the ray tracing for saving valuable time. Well you could but then the master beauty are missing the reflections. Now you have to do this manually, but missing the “single” option from 2.49, you have to deselect all render layers except the one you want to render and render only that one. Keep on doing that for every render layer you need a different setup for.

Another example is if you need to make a special mask. On a car you maybe need to render a separate mask only for the cavities between parts in the chassis. You have to make two new materials, solid white and solid black and assign that to the desired polygons. You cannot do this without loosing the previous material and its polygon assignment.

A work around would be to make another scene. That way you can assign different materials and have completely different render settings. But this comes with other problems. To make an object have another material you cannot do that without making it a single user of everything, that means if you have to change animation or even only location of an object in the original scene, it is not carried over to the other.