I think point (2) is the most important of those. When the Fortune 500 outsources to one of the bigger outsourcing firms like those you mentioned, they're outs

I think point (2) is the most important of those. When the Fortune 500 outsources to one of the bigger outsourcing firms like those you mentioned, they're outsourcing the whole process of developing software from requirements gathering to testing and the final output is not just working software, but a full trail of documentation for accountability. You're not getting that from rent-a-coder.