Mumphrey,
To put my opinion in context, let me explain that I am close to completing the PADI DM program. All I need is to participate in a continuing education course as part of the internship; hopefully offshore NC next weekend.
IMO there are two important factors to determining the best DM instruction for yourself.
Environment Look, to complete your training in the environment, both dive conditions and economics that you intend to DM in. There are a wide variety of conditions and situations where you could put your DM skills to good use, they tend to require different skill sets. IMO taking an academy DM course in the warm, clear water of the Florida Keys does not prepare one well for my reality, which is OW dives in cold quarries with poor visibility and the ever-present silt. Conversely the course I took here did not prepare me well to act as a DM on a dive boat. Not only do the diving conditions very but also the economic conditions of the operation youll be working with.
Instructor(s) Look for a training environment were youll be exposed to different instructors in the environment you intend DM. The instructor(s) have a dramatic impact on the quality of your training. I like the idea that I was exposed in one way or another to ten different instructors and dive masters during the DM program. While all of them meet the PADI standards, there are vast differences in diving skills and teaching styles. During the training, Ive observed an instructor that is a butt head that I dont even like to be around, a bottom dwelling instructor that I can follow around the quarry from the silt tracks, several good instructors, and several great instructors. Ive seen instructors that go to great lengths to make the OW dives a truly fun and memorable experience for the students and others that have not figured out that diving is a sociable activity. IMO anyone that takes the program with any single instructor is shortchanging himself or herself. They all have different strengths and weaknesses, in the water, with personal skills, and with the economics of the dive operation; they all have something you can learn. For whatever its worth, Ive observed that Instructors that were trained and teach OW in the cold dark quarries are not only better divers but better instructors in that environment than Instructors breed in the warm, clear, silt less waters of the Caribbean.
Mike