First... good for you for wanting to broaden your knowledge! Second, you are comparing a language (Python) with a web framework (Ruby on Rails).
I think your best option is to try a few different frameworks in both Python and Ruby, do the same fairly simple task in each, and only then pick which one you'd like to learn more about. Rails is nice for Ruby, but it's not the only one out there. For Python I like Pylons and Django.
Pros and cons: Ruby is a little cleaner, language-wise, than Python. Python has a much larger set of modules.
Is it worth learning? Yes, to both Python and Ruby.
