Whatever its merits, Adobe's Actionscript 3 presents what may be a unique opportunity to explore the consequences of typed versus untyped languages, because it is pretty much a strict superset of javascript, with all the syntactic benefits/overhead of strict type declarations, declarative casting, etc.
What this makes possible is comparing the same code written both ways, while factoring out essential language syntax.
This causes me to wonder if there is any quantitative evidence about the real benefit of strong typing in particular for error checking during compilation, with respect to error rates, programming productivity, and code volume; or are our perspectives entirely based on speculation and conjecture? Are there any other languages that can be used both ways (not counting old-fashioned VB - not being a highly respected language either way.)
I've spent significant time with both languages, but haven't conclusively decided which way I prefer, and I'd rather not add to the anecdotal evidence - I'm looking for objective information.
This is one of the great religious wars in programming, exceeded only perhaps by the conflict between the one True Editor EMACS, and the evil spawn of Satan vi.
Basically, if a program written in a dynamic language is correct, then it can be converted to a statically-typed language and still be correct, and vice versa. The advantage of a truly statically-typed langfuage is that bugs which would show up at run time in a dynamic language can be identified at compile time in a statically-typed language.
What often gets neglected in these situations, though, is that statically typed languages generally have escape hatches (like typecasts), and apparently dynamic languages can use type inference to infer, and treat as statically typed, the types of apparently dynamic expression.
What's really important, under the covers, is the programmer. If the programmer thinks the program right, then it'll be right in either a static or a dynamic language. I'm not aware of any good experimental evidence that either one is more productive or more prone to errors in practice.