MMAWeekly has an interesting article on the safety differences between a cage and a ring:
But this isn’t settled yet. The statement that a cage is safer than a ring is not one of architecture or physics. It’s an argument used to combat a particular perception. The problem with this answer is not one of veracity; the problem is one of phraseology. A cage is a place where you keep an animal, in many cases, a dangerous or vicious animal.
This is a pretty broad statement to make. I’ve kept my sister locked in a cage for years and she’s the most docile person I know. It wasn’t always this way though … it took me years to get her to stop all her screaming, wailing, and crying. But fortunately the soothing effect of her cage finally took care of my problems and now she just sits in there rocking back and forth quietly.