Which distro do you think is better and why? (ie: RedHat, Mandrake, Suse, etc...support, updates).
What 3D/2D software have you tested with it and what were the results?
Well, thats a question that can't be answered really, depends in what you want from your distribution. Probably the ones you named are the most user friendly ones. If you don't know anything about linux and you want to use Maya, the best thing to do would be to use the only supported distribution, and thats redhat; but I would use another one. Personally I use Gentoo, but is for more advanced users, probably you won't like to start with this one. Suse or Mandrake should be ok and you shouldn't have any problems using any 3D apps in your distribution of choice.
here's a site for you to take a look:
http://www.distrowatch.com
if you're completely new to linux, you can try it out without installing by downloading a knoppix bootable cd:
http://www.knoppix.net/
What 3D/2D software have you tested with it and what were the results?
Maya, Shake, Houdini, Prman/RAT
They all run significantly faster than their windows counterparts(gui and overall program). I would say 15-30% depending on the app.
Bear in mind that Maya is not qualified for RedHat 9.0, although it will work with some minor tweaks. If you use 7.3 (qualified, but old), be sure to check for security patches and install them if they exist.
Actually I'm thinking of trying Suse 9.0 with Maya to see if there are any advantages or disadvantages on that distro. It interested me since Sun is now backing the company.