Not really a con. The PDR guy may need access from the inside, so depending on dent location, they will take apart a good portion of the interior to get access. On doors, many can remove the dent through the window channel.
I don't remember the name of the PDR company, but it's probably Dent Pro or Dent Wizard that did my friend's car. They drilled an access hole that was later plugged in the door to get get out a dent near the edge.