I'm a C# .NET developer and I work on mostly ASP.NET projects.
I want to learn a new programming language,

to improve my programming skills by experiencing a new language, 
to see something different then microsoft environment,
and maybe to think in a different way.

I focus on two languages for my goal. Python and Ruby.

Which one do you offer for me ? 
Pros and cons of them on each other?
Is it worth learning them ?

EDIT : Sorry I editted my post but not inform here, 
Ruby on Rails replaced with Ruby.
I'd get in on Ruby. Seems to have a larger (or at least more active) community, the pace of new projects & continued development is second-to-none, and the learning resources seem to outnumber & outpace those of Python. I could be wrong, but these are my impressions.
Python or Ruby for a .NET developer?