Hey there Remy B., as an Instructor Trainer for PDIC, I would first like to say congratulations on your Open Water certification. Second, your instructor makes a good point, which goes along with the philosophy of PDIC, in an emergency it is rarely one little thing that causes the problem, it is usually multiple things that cause emergencies. Also I think that it is a great idea to take the rescue course through multiple agencies. First you will see different teaching abilities between the instructors and you may learn multiple ways to handle the same situation. Secondly, having already completed the PDIC Open Water course, you will already have a heads up to the PDIC Rescue course, being that you learned several rescue skills in Open Water. For your question, as far as what each offers, PDIC will most definitely be more challenging (additional prep skills), extra swims being an example. I will also vouch for the PADI course (also being an instructor MSDT), the material and presentations that you will see (if traditional class room is taught), is very well laid out and a lot of good information will be giving. It is also easy to learn from the material itself (methodically presented presentations). Being our store also has SDI instructors on staff, I have reviewed the training material and the standards and procedures of the rescue course. A common theme is repeated here also and it is very comparable to PADI's Rescue course. Lastly, is SSI's Stress & Rescue Course. In 2010, I worked for another dive shop (prior to opening my own), and this shop, like mine, trained for different training agencies. One of these agencies was SSI. The shop owner being a SSI Instructor Trainer was big on allowing all of his employees and instructors sit in on his classes, to increase their knowledge of diving. I always enjoyed these opportunities to learn and to compare other training agencies that I taught for. The SSI Stress & Rescue course can hold its own with the others. When comparing courses, those you listed, all are comparable to others, with some minor differences (depths, ratios, added skills, scenarios, etc.). As far as order, I would definitely start with PDIC, then maybe SSI (or PADI), then PADI (or SSI), then end with SDI. Now with all that being said, as I'm sure others will agree, the instructor makes a big difference in the equation. Welcome to the world of diving, and who knows, maybe all these classes you are taking will help build a good source of knowledge for you one day, if you decide to continue on to be an instructor. Happy Diving. By the way, our shop is headed to CURACAO on November 1st, maybe we will see you there.