First of all, being European there may be a different point of view... I am CMAS certified at level III (3 stars); to get the third star the training tooks several months, each week lessons in the pool and classroom, sea dives during the week-end, day and nigh; so I am a bit suspicious when I hear about "just a few dives and here's your brevet".
I say suspicious because there are a tons of things you can do in pool/sea, many exercises you can try and endless things to learn. I remember chatting with PADI friends about how a first stage worked ("There is *really* a spring in the regulator? What for?").
But it is also true that 99% of the times, you will not need put in practice what you have learnt unless there is some real emergency; and since equipment is quite reliable (IMHO) people have to do really stupid things to put themselves in danger.
So, perhaps a more "straight" approach is more time-efficient: if you learn the absolute minimum and off you go, it will do for 99% of your dives. Just to make an example, it is like to explain "Ascent at no more than 10 meters/minute" as an absolute rule as opposed to spend a few lessons to explain that it is not the speed that matters, but how differential pressure change, therefore the optimal ascent speed is related to depth and it isn't fixed... Which is better?
My opinion, for what it is worth, is that PADI has a different approach compared to CMAS with references to learning, but I would never say it is bad, just different: more "tools/technology oriented" as opposed to "knowledge oriented", more "practical" as opposed to "theoretical". You will always learn what you have to do, but not always why and how certain things work.
The only thing about PADI which I really dislike (but now CMAS has changed and adopted the same approach so ...
is the idea to "fragment" the knowlegde in a number of courses that could really be merged together. It seems to me more a commercial (pure $$$ driven) policy than an good way to teach people: there are so many of them that we used to joke (in the past) about the fact PADI offers "Diving on Bank Holidays", "Diving with the mother-in-law", "Diving under the rain", "Diving after lunch" and so on. But like I said, now CMAS is doing the exactly same... Long gone are the days when there were "three stars/courses for divers" and "three stars/courses for instructors" (and those courses took a lot of time).
On the other hand, I fully agree that certain skills/notions should be kept separated: an example is Nitrox training, because clearly if you are not: a) interested in Nitrox, b) have (or plan to buy) a Nitrox-compatible computer and tank, c) have a buddy with the same interests/setup you will never dive with enriched air, so what's the point of spending money and time in that (except for giving a few bucks to the diving school, of course!).
In this respect, I find very difficult to accept the fact that Nitrox is mandatory to get any advanced training. Will a dive handle better an emergency just because he/she has a tank filled with Nitrox? And if he/she has to give air to another diver in danger (regulator in free-flow, hose cut, whatever...) and that particular diver is using air (as in standard air) what deco profile has to be used? AFAIK, there is no answer to this question.
Cheers,
DareDevil
