I too went to Medicare.gov and went through their computer program for our state and community to see which Part D program was best for us.
Some people are in Medicare Advantage programs that group all plans together. The hospital group controlling healthcare in the region north of my home has prohibited any of their hospital owned doctors and affiliated hospitals from accepting any patients with Medicare Advantage--1700 physicians and nurse practitioners in total.
That means 10's of thousands of patients have had to change doctors and watch carefully that they don't go to any of the affiliated hospitals that are not accepting the Advantage plans. Most will end up in HCA hospitals throughout 7 states. I would assume the disagreements were to do with the rate of payments--money issue.
I'm type II diabetic, and have chosen to go on insulin with a pump. Because I'm on a pump, Medicare Part B covers insulin and all my supplies. My doctor has to "code" my prescriptions in a way that Part B pays--saving me big money. Insulin is now $255 per tiny vial--up dramatically from the past. If I wasn't on the pump, my insulin would be $1770 for 3 month supply--and my co-pay would be substantial.
Needless to say, it's very important that you pick the right program and understand what your specific needs are.