I'm also considering learning either Python or Ruby, but was leaning more towards Python due to its strong math libraries. Does Ruby have equivalent capabilities for math and science?
No SciPy is amazing and I wish ruby had something like it. Its also got a lot of C so its pretty fast though you interface with it in Python.
Ruby is the perfect scripting language, and you'll be surprised at the sheer utility of having something the ability to use something like this. Forget the web side of things; just he ability to whip up a quick throwaway script (to automate office tasks, calculate forecasts, do complex eng calculations etc) gives you a massive advantage over others in your field.