Why Ruby on Rails?

The stack on the left is the Java books, the stack on the right is the Ruby books. The same breadth of material is covered. Well almost, there are on-line references for things like XSL, not covered in the Ruby books. But other than that the functionality is the same. So which stack will be easier to keep in my head? The choice is easy.

Check this url: http://www.garbett.org/?q=node/25#comment-13
Shawn gave a great comparision of Rails with Java.