Honestly, as far as metaprogramming facilities go, Ruby and Python are a lot more similar than some of their adherent like to admit. This review of both language offers a pretty good comparison/review:
- http://regebro.wordpress.com/2009/07/12/python-vs-ruby/
So, just pick one based on some criteria. Maybe you like Rails and want to study that code. Maybe SciPy is your thing. Look at the ecosystem of libraries, community, etc, and pick one. You certainly won't lose out on some metaprogramming nirvana based on your choice of either.
