I find this idea interesting...shopping the program/agency I mean.
I don't have recent SSI experience, and I have sero PADI experinece
my 2 cents worth:
- I suspect that as many others have suggested, the instructor is the biggest variable. Someone that knows the stuff and is good at it...but it also has to be someone that you can connect with personality wise....
- Next up is probably the shop's SOP. Could be a lot to do with their set-up. Their pool, the locations they choose for their checkout dives, how the coordinate and set-up the course, etc...
- Next up is likely the certifying agency. Some probably have much better online "bookwork" than others.... but I still suspect that the standards and practices are pretty much the same.
Years ago when I was actively collecting cards, I always assumed that all the programs were pretty close to mirror images of each other....with the only real difference being the presentation.... the books would have different looks and feels, and might be organized a little bit differently. (yes, back then we supported the paper industry). I never really knew if my assumption was correct. I was SSI and my best dive buddy at the time was die-hard PADI and he and I would have discussions about it but I could never really understand any difference fundamentally.
I went through SSI, not by design, just by location. The dive shop near where I lived at the time when I decided to get certified was a one-man-band shop and he was teaching SSI. When I moved to a different city, the closest/biggest/seemingly most active shop happened to also be an SSI shop. There I did advanced OW and lots of other courses, all the way up to the now-defunct Divecon. That's also where I started with IANTD with nitrox. That was when nitrox was technical and none of the recreational agencies were doing it.
It was the same with IANTD. Later when I got into doing tech stuff, it seemed that with every move my choice was IANTD
Anyway, fast forward a couple of decades, and I was finally exposed and trained through another recreational agency, SDI. I did a refresher while my family did their OW certification. It was a very different experience from what I remember from SSI all those years ago. I doubt that' it's useful info though, because there was so much time between the experiences.
Regardless
Generally, I would say that the old paper books and the theory stuff they taught back in those days with SSI was far superior to the pared-down reader's digest version of today from SDI. That's an apples to oranges comparison though and I'd bet that the SSI stuff of today is more or less the same as SDI's stuff.
I think overall the face-to-face instruction in the pool and OW was much better recently with SDI than it was for my original OW cert, anyway. Maybe to a lessor degree it was better than teh SSI advanced stuff I did too, at that 2nd shop. My guess is that it was the instructor who made the difference.
but
How much of that is standards from the agency vs instructor? How much is instructor vs the shop's SOP?
In our case, the pool instructor was only fairly recently certified but she was good. Was that the agency's doing? The shop's doing? or her natural ability and hard work? Hard to know.