It's going to be hard to say much without starting some biased flame war, since in the end there's nothing that one framework can do that another can't, really.

All of the languages mentioned above have pretty good ecosystems around them. I think Ruby's is the strongest at the moment, but if you're more of a python guy no harm in that :P.

Honestly I learn as much as I can, and as such have done at least a little bit of dev work in all of the above languages plus some :P. Never hurts, and you'll be able to make a much more informed decision yourself afterwards.