As previously noted organizations follow a minimum standard set by the scuba industry and the organization, they differ less than you might expect. If they did not establish these themselves I am sure the feds would have stepped. Instructors however differ a lot, and you should talk to the instructor you will be taking the course from and determine exactly what will be offered and how you feel about them as an individual. Finally, some instructors add significantly to the standard course (and may also charge more). You should know exactly what you are going to get for your course before beginning the course. For me its ease I love teaching and I love to dive. We believe teaching small class sizes ensures each participant gets the most enjoyment and instructor attention possible. This formula of one on one attention maintains our 100% safety record and reputation for quality of training. This has made us well known for our quality in diver training with a personal, friendly service.