Don't forget about rendering time. If your animation takes 10 minutes to render each frame then a 30 second animation will requires 150 HOURS of rendering time!
A couple of times our team had to use Scanline rendering because we didn't have time for Mental Ray. This year we planned a little better (and borrowed an 8-core PC) so we were able to use Mental Ray on our safety animation.
Complicated geometry, caustics, fancy lighting, shadows, reflections and transparent objects increase rendering time.
Most of the big studios have rendering farms; rooms packed full of cheap PCs that do nothing but render frames. It's not to difficult to set up network rendering with Max. I don't know about Maya.
But you can do beautiful work with the Scanline renderer:
http://www.mrcad.com/blog-images/scanline-render.jpg
http://raph.com/3dartists/forums/attachments/336.jpg
http://3dnews.files.wordpress.com/20...-furniture.jpg