Putty or Silicone?

Which is best to use when installing a drain in an acrylic tub, plumber's putty or silicone?

I would go with putty the no staining type.

Thanks, cwhyu2, for the quick reply, and Terry too for the picture!

I just want to point out in the ongoing "putty vs. silicone" debate that at least with no-calk shower drains, both of the mainstream manufacturers (Oatey and Sioux Chief) specify using SILICONE under the flange, not putty. As such, the debate should be moot if people want to follow what the manufacturers suggest.