Oh, and regarding JRuby versus Python 3...yes, if Ruby 1.9 smokes Python, and JRuby is faster than Ruby 1.9, then JRuby should smoke Python even more. I have not done the comparisons myself, though.
I know some of the implementations there use native libraries that are built into python but only available via RubyGems for Ruby, like numpy. That makes it less of a language shootout (at times) and more of a "who ships the best C libs" shootout.
I believe MRI is generally faster than Python now when they're doing roughly equivalent work in Ruby and Python.
Except that Python has scipy,numpy and cython in its camp. I have spent the last six months of my life making Python code run faster. You can write slow code very quickly in Python. If your users complain about it being too slow you can implement some critical sections in Cython. (again with very minor changes). That being said there is a overhead to calling functions in Python which I would like addressed. (Dictionary lookups were three times as fast as function calls when I measured them).
