Is he a GP or a Specialist? From what I know, the list of best Doctors is full of specialists, not generalists. I am yet to hear someone recommending a General Practitioner because they have broader knowledge. It is always Specialists who are focused on one domain and one domain only. Not saying specialists don't have knowledge about other things medical-related. They do but their knowledge is limited. Just like my knowledge about firewalls and networking is limited because I focused on development.