The skills taught are basically the same. SSI's main difference from PADI has nothing to do with the divers, it is in administration. SSI requires their instructors to be shop affiliated where PADI instructors have no such requirement. SSI also utilizes a total diving system, which basically attempts to have new divers purchase as much equipment from the get go as possible. The idea behind the total diving system has merits as the more the student has invested in learning the course, the more likely the student is to continue diving after training. The differences in the much touted in "Advanced" open water is not as extreme as others try to make it, as comparing SSI's specialties and PADI's specialties are like apples and oranges. Look at the numbers of dives required to achieve the specialties in each program, and the ability or inability to combine courses during the same dives and you'll find the answers. In example, PADI does not allow combining courses during a dive with the only exception being nitrox. PADI requires 4 dives for a Deep certification versus 2 with SSI. They are both fine courses that will teach you, with a good instructor, what you or your friend are wanting to learn. And no, the depth limit "recommendations" are the same for both agencies; 60 feet for open water "until training and/or experience increases; 100 feet for those with training or experience. SSI AOW does require the diver to have 25 dives a requirement not mirrored by PADI. Both SSI and PADI Master Scuba Diver require 5 specialties, Rescue and 50 dives, a card reflective of the diver's accomplishment and pursuit of training.
