>But you'll also get significantly better productivity out of python, assuming equivalent knowledge.

Why? What is python doing to get you better productivity? As someone who is certainly not an expert at python, but used it as my perl replacement for a few years I feel like I am as productive in python as I am going to get. I was just as productive in go after two days of playing with it. The only reason I can see to use python is if it has a library/framework go doesn't.