> difference between intermediate and advanced is the ability to move from discussing only facts to making a coherent argument.

This is a brilliant point and never thought about it this way. I've spoken spanish for 5 years but i've always felt some things lacking when i've tried to make an coherent argument about politics for eg. One more thing i'd like to add is 'humor'. If you can make jokes or be sarcastic to natives in their language, then you've definitely crossed another barrier.