Hello,
Funny this question found me during my search. I was asked this question by our German QA consultant for our newest product in clinical trials. He ha never received the answer before meeting me, but it was indeed the correct answer. The key difference between 13485 and 9001 is that 9001 requires customer satisfaction monitoring and measurement, in 13485, as the products are medical devices that have already gone through rigorous clinical trials and has been proven to perform to requirements, this standard addresses customer feedback (IE: complaints product recalls etc..)
I hope this helps