When using Python I feel the least resistance from the language, you can do a lot with a little code. Problem is, when the system grows you begin to miss the checking that static typing provides (esp. when doing refactors).
When coding in Go I feel that there is a little productivity lost upfront, but when your script begins growing and starts to look like a "serious" project you feel more confident changing your old code. This is because some kind of errors are caught by the type system before doing manual/automated testing.
And I'm talking about personal projects where I'm alone, this could be more important in projects with several coders.
(I favor this and explicitly annotate most of my types in Haskell and Scala. Makes reading easier. But I did occasionally find it annoying in Java when it was mandatory.)
They make cleaner, and therefore, more readable code. That is the main thing people want from dynamic typing anyway. It's really not very common to change the type of a variable, and a statically typed codebase is more predictable, and therefore easier to manage.