I was under the impression that these were the most commonly sought after agencies for certification. That impression was not formed from having done in-depth, quantitative research, however, and it's very likely that I'm mistaken. I checked out your comprehensive list and have to admit that I didn't realize half of those agencies were in existence. I also realize that my initial question was far too broad and that I should have been more specific. If my list is really skewed, I apologize - I'm not very knowledgeable in this area (which is why I asked the question in the first place).
If you look in terms of market share, the market for recreational training is split up like this:
1) PADI
2) everyone else
It's that simple. Most agencies that teach recreational diving are PADI clones and/or borrow heavily from PADI's didactic methods. Yes, they have all needed to add one thing and take one thing away and change the logo so they don't get sued for copyright infringement, but in some cases the differences are literally just that.
There are a few agencies, all of which are niche players, that do things very differently but the basic course content between all of the major agencies differs mostly in nuances and emphasis. As divers, we sometimes clamp onto some difference between agency A and agency B and argue heatedly that the differences have a HUGE effect on quality or the results at the end of the day but it's simply not true.
The instructor, on the other hand, makes a HUGE difference. Standards are just a check list of things that the student needs to learn. You can't build quality training with a check-list. You build quality training when you turn that check list into meaningful knowledge transfer and meaningful practical in-water experience. And the agency can't do that. They only wrote the book. It's the instructor who delivers the course.
If you take 100 divers from 30 different agencies and put them all the the water together then you *might* be able to identify where one or two of them were taught, but mostly you would be guessing. If the group of divers has 20 dives or more of experience then the only differences you're likely to see at that point are differences in individual talent and personality.
For more advanced to borderline technical training, which internationally-recognized agencies might be better options?
The one who has the best instructor in your area.
I've gone the PADI route so far and don't have any complaints, but the more advanced training is an area where PADI seems to back off and where other agencies may be very strong. Specifically, I'm looking at advanced nitrox, light deco, and courses that teach how to handle more complex environments and conditions.
When it comes to these kinds of activities, your choice of buddies after certification (by a good instructor) is likely to make a bigger difference to how proficient you become than your choice of agency. Personally, I did my technical training through IANTD. I liked the idea of going with an agency with a tradition of technical diving and I knew a good instructor. What I discovered about IANTD is that their written materials suck beyond belief as compared to the PADI materials (at least when I took the course). I've heard the same about some of the other major players in the tech world. What ever way you go, one thing is essential. You need to hook up with good, experienced, tight, CAREFUL buddies after you've done your training and get out there to do the dives. If you don't do that, it won't matter much what agency's logo is on your card.
R..