Several comments:
1. Take AOW from SSI or PADI. It mostly doesn't matter, but take it. It's like a union card: It might not mean much really but it gets you access to things you wouldn't have otherwise. E.g., I think most shops that dive the Blue Hole in Belize require AOW.
2. I can't speak for SSI, but with PADI the dives you do as part of AOW are dive 1 of 2 for the specialty. In your case, I suspect what that means is if you do AOW with PADI, SSI might not count any of that work toward specialties. PADI wouldn't do the reverse. But do you really want a bunch of other specialty certifications? Most don't do anything for you. Exceptions would be nitrox, dry suit, and possibly deep. All three gain some traction in terms of what you're "allowed" to dive. Peak performance buoyancy can teach good skills, but there is no sense paying for the card.
3. Once you commit to the "pro" levels (DM, Instructor) it is painful to switch to another agency. Not impossible (it happens all the time, and agencies have "crossover" courses specifically to do this). But costs money and time. Prior to that, everybody pretty much has equivalencies set up so your training in one agency qualifies you for training in another agency. In my case, my OW certification is YMCA because they frankly did training right in 1985. My AOW was NAUI because the instructor was a friend and colleague and did it for me at no cost other than paying for the card. (He even gave me the books.) Rescue (and beyond) was PADI because the LDS is PADI and convenience mattered at that point in my life. But PADI didn't not bat an eye at my YMCA or NAUI certifications.
4. Mastery is edu-babble. (And I speak from a lot of experience being forced to listen to edu-babble.) PADI was founded by teachers and still has that sort of ethos going on , so it's not surprising. It does not mean the same as being, say, a master in your trade. It's more along the lines of getting a driver's license if you've "mastered" driving. Just because you've got one doesn't mean your better than the average driver.
5. In Peak Performance Buoyancy there is more done than in OW. The following are not inherently involved in OW training but are required for PPB:
*Estimating and rigging your own weight system. OW somebody might just hand you weights they guess might work.
*Adjustment of weight for neutral buoyancy is a harder-core requirement, though IMHO it should be done in OW as well. (But you're still starting with somebody else's guess as to how much weight you need and then adjusting from there.)
*The hover skill is timed; 60 seconds. This is not done on open water dives in OW training, though it is in the pool. There is also a limit of no more than 3' variance in the hover. And that's with no kicking or sculling allowed.
*Adjust depth using breath control. Not required in OW.
*Kick efficiency should be judged.
*Hovering in different positions is required. E.g., I'll point to an object and have the student hover nose-down over the object.
Now arguably all of the above could or should be included in a good OW class (and I won't argue that). But they're not the same standards as stated for OW. I do some of the above with my OW students, but not all. E.g., I don't do the odd position hovers or timed hover in OW.
1. Take AOW from SSI or PADI. It mostly doesn't matter, but take it. It's like a union card: It might not mean much really but it gets you access to things you wouldn't have otherwise. E.g., I think most shops that dive the Blue Hole in Belize require AOW.
2. I can't speak for SSI, but with PADI the dives you do as part of AOW are dive 1 of 2 for the specialty. In your case, I suspect what that means is if you do AOW with PADI, SSI might not count any of that work toward specialties. PADI wouldn't do the reverse. But do you really want a bunch of other specialty certifications? Most don't do anything for you. Exceptions would be nitrox, dry suit, and possibly deep. All three gain some traction in terms of what you're "allowed" to dive. Peak performance buoyancy can teach good skills, but there is no sense paying for the card.
3. Once you commit to the "pro" levels (DM, Instructor) it is painful to switch to another agency. Not impossible (it happens all the time, and agencies have "crossover" courses specifically to do this). But costs money and time. Prior to that, everybody pretty much has equivalencies set up so your training in one agency qualifies you for training in another agency. In my case, my OW certification is YMCA because they frankly did training right in 1985. My AOW was NAUI because the instructor was a friend and colleague and did it for me at no cost other than paying for the card. (He even gave me the books.) Rescue (and beyond) was PADI because the LDS is PADI and convenience mattered at that point in my life. But PADI didn't not bat an eye at my YMCA or NAUI certifications.
4. Mastery is edu-babble. (And I speak from a lot of experience being forced to listen to edu-babble.) PADI was founded by teachers and still has that sort of ethos going on , so it's not surprising. It does not mean the same as being, say, a master in your trade. It's more along the lines of getting a driver's license if you've "mastered" driving. Just because you've got one doesn't mean your better than the average driver.
5. In Peak Performance Buoyancy there is more done than in OW. The following are not inherently involved in OW training but are required for PPB:
*Estimating and rigging your own weight system. OW somebody might just hand you weights they guess might work.
*Adjustment of weight for neutral buoyancy is a harder-core requirement, though IMHO it should be done in OW as well. (But you're still starting with somebody else's guess as to how much weight you need and then adjusting from there.)
*The hover skill is timed; 60 seconds. This is not done on open water dives in OW training, though it is in the pool. There is also a limit of no more than 3' variance in the hover. And that's with no kicking or sculling allowed.
*Adjust depth using breath control. Not required in OW.
*Kick efficiency should be judged.
*Hovering in different positions is required. E.g., I'll point to an object and have the student hover nose-down over the object.
Now arguably all of the above could or should be included in a good OW class (and I won't argue that). But they're not the same standards as stated for OW. I do some of the above with my OW students, but not all. E.g., I don't do the odd position hovers or timed hover in OW.
