You're absolutely right. I acknowledge that PADI permits primary donate. I'll edit my post. But a friend's PADI OW instructor wouldn't teach her with a 40" hose, and insisted on PADI's textbook configuration. Whether or not it's in standards, not a few shops and instructors have interpreted their pictures as "rules." My pointing out that the standards allow different equipment configurations didn't make them budge.
Some instructors don't fully grasp what they are doing. (present company not included, I'm talking in generalities here).
I'm guessing that the ones who look at the "comic book" version of the course and don't bother really delving into the details of what they are doing will also look at the pictures of students kneeling on the bottom and conclude, despite standards explicitly stating otherwise, that they are not required to teach neutral buoyancy to their students beyond struggling through the couple of minutes of "sort of hovering" that I'm sure they find to be the most difficult and challenging things to teach.
My point being... also to the OP... that the instructor is EVERYTHING at this level. There are VAST quality differences in the delivery of any course from one instructor to the other and nowhere does it show up more than at the novice level.
As for PADI or SSI..... SSI started life as a PADI clone. They copied the course and changed only the minimum number of things to avoid copyright infringement. Fairly recently PADI has been innovating again--as John pointed out--and at some point SSI will follow suit, because following is what they do best, but in terms of basic learning at this point in time, either system will do provided you can find a competent instructor.
I want to say that last thing again.... "provided you can find a competent instructor". NO system, regardless of how good it looks on paper is worth it's weight in doggy drool if your instructor doesn't know what they are doing. Every system has good instructors who know how to use the system to teach well and every system had bad instructors who look for the wiggle room to justify being an incompetent bozo who will put you, as a novice diver, at risk.
Making this distinction is difficult if you have no frame of reference to go on, so you absolutely NEED to get references and recommendations. This is one case where shopping around does make a huge difference.
R..