When it comes to scripting languages, the objective differences are very nuanced. Largely, it depends on what you want to do. Python, for example, is extremely popular in the data sciences. A complementary example for Ruby would be rapid application development with Ruby on Rails, a web framework that allows you to build web applications very quickly. Another example would be building an API using Ruby's Sinatra library. Python also has web frameworks, so it's not as if Ruby has an exclusive claim to this benefit, but many developers find tools like Ruby on Rails and Sinatra very satisfying and beneficial to work with.

My recommendation would be to give Ruby an honest shot. Don't make the mistake of simply trying to write Python code using Ruby. Really dig in to what makes Ruby, Ruby. If you enjoy it, then you've added another language to your tool belt. If you don't, you might walk away with some ideas about development that you can apply to Python.

Ruby and Python are languages.

Rails is a framework.

So it is not really sensible to compare Ruby on Rails vs Python.

There are Python Frameworks out there you should take a look at for a more direct comparison - http://wiki.python.org/moin/WebFrameworks (e.g. I know Django gets a lot of love, but there are others)

Edit: I've just had a google, there seem to be loads of Django Screencasts.

There are probably two major differences:

Ruby has elegant, anonymous closures.

Rails uses them to good effect. Here's an example:

class WeblogController < ActionController::Base
  def index
    @posts = Post.find :all
    respond_to do |format|
      format.html
      format.xml { render :xml => @posts.to_xml }
      format.rss { render :action => "feed.rxml" }
    end
  end
end

Anonymous closures/lambdas make it easier to emulate new language features that would take blocks. In Python, closures exist, but they must be named in order to be used. So instead of being able to use closures to emulate new language features, you're forced to be explicit about the fact that you're using a closure.

Ruby has cleaner, easier to use metaprogramming.

This is used extensively in Rails, primarily because of how easy it is to use. To be specific, in Ruby, you can execute arbitrary code in the context of the class. The following snippets are equivalent:

class Foo
  def self.make_hello_method
    class_eval do
      def hello
        puts "HELLO"
      end
    end
  end
end

class Bar < Foo # snippet 1
  make_hello_method
end

class Bar < Foo; end # snippet 2
Bar.make_hello_method

In both cases, you can then do:

Bar.new.hello  

which will print "HELLO". The class_eval method also takes a String, so it's possible to create methods on the fly, as a class is being created, that have differing semantics based on the parameters that are passed in.

It is, in fact, possible to do this sort of metaprogramming in Python (and other languages, too), but Ruby has a leg up because metaprogramming isn't a special style of programming. It flows from the fact that in Ruby, everything is an object and all lines of code are directly executed. As a result, Classes are themselves objects, class bodies have a self pointing at the Class, and you can call methods on the class as you are creating one.

This is to large degree responsible for the degree of declarativeness possible in Rails, and the ease by which we are able to implement new declarative features that look like keywords or new block language features.