[brianpgordon]

Python and Ruby are great for building an MVP, and they'll take you a long way, but they're probably unsuitable for a high-stakes codebase like a financial system. When bugs are absolutely unacceptable, you need all the help you can get from static analysis.

And (don't crucify me HN) I think dynamic typing rapidly loses its allure as your codebase grows large and "enterprise." The advantages in rapid prototyping and easy changes start to be overshadowed by the increasing burden added by unexpected side effects any time you change something. In Java, if I change an interface then I can find every client of that interface with one click and make sure each one is not broken by the change. The same is not true of JavaScript code; changing the valid inputs of a function can break things scattered around the code, and you won't notice unless you use a particular feature 3 times in a row on a waning gibbous moon.