I disagree slightly. A completely idiotic partner can totally take my focus off of the patient (somewhat) and onto parenting him.
I had a guy dump out the drug box a couple of weeks ago, and spike the IV through the med port on the bag, and say some stupid things to the patient.
That particular partner doesn't get to do anything anymore except carry stuff, lift his end of the stretcher and drive. That makes me a slower medic overall, since I have to stop the interview to get vitals, hang my own IV bag, etc. And I think speed and efficiency matters.
I disagree with the thought that you're only as good as your partner lets you be, though. You just need to know how much you have to control your partner's actions too.
^^^^^^
This
Your partner doesn't necessarily affect WHAT care is provided, but it sure as sunshine affects the delivery of said care, and delivery of care is part of quality care.