Don't pick just one!
Over reddit, a lively discussion on which language, Python or Ruby, is faster. In the comments, the usual suspects and the expected opinions. Except for Slava Pestov's (of Factor and jEdit fame), whose pointedness is on par with his stature as a programmer. I concur wholeheartedly with his opinion; in particular, his observation that
Slow language implementations are fundamentally less expressive because they give you less freedom in how you implement your code. You have to optimize […] a slow language is by definition not very expressive because it constrains your coding style […]
is right on the money. To which I'd like to add: when out shopping for a programming language, caveat emptor and choose a compiled, native one. The usual argument about turnaround time and programmer productivity is bogus: after all, machines were getting equally faster both for dumb interpreters and multi-pass compilers. And if what bogs you down are the compile-time errors, an interpreted language will not make you any more productive: as much as you'd like to, you cannot sink the costs of debugging and failing at execution time.