I personally believe that the Advanced Open Water Class - from PADI at least - is an add-on to the Open Water class - so it is Advanced OPEN WATER, not ADVANCED open water, if you see the difference in the emphasis. I think the name is often wrongly contstrued as an advanced diving class, when in fact it is a simple advancement of the basic introductory level course.
Where possible, I like to have my students start a PADI AOW class as soon as they are able after completing Open Water - a chance to expand on basic skills already acquired during the open water class. Further tips and techniques that it is simply not possible to fit into the 4 or 5 day standard open water course.
The semantics of mastery and four day courses have been debated at length and let's not get into that here, but I accept that any people have a different perspective on what constitutes the AOW class - at least from the PADI schools. The Navigation dive and Deep dive expand on techniques and knowledge learned in the OW class. Peak Performance Buoyancy is an invaluable dive for the inexperienced diver and I do not see these things as task loading, because the fundamentals of these skills should have been mastered - not to perfection but to a point of comfortable repetition in the Open Water Class. If a student finds that the AOW is task loading, then potentially their OW class was not up to required standards.
I am realistic - I accept that there are poorly trained instructors who poorly train divers. This should not be but it is the simple fact of life at the moment. The arguments are extensive and have been repeated here ad infinitum and ad nauseum on these forums but an instructor is also required to evaluate a student for dive skills and theory before commencing an AOW class. This might be a short pool session or a check dive, depending on the instructor and or the dive centre they work for. A student who is not ready to commence "Advanced Training" should be remediated to correct any mistakes their OW instructor may have made.
I agree that you should seek a good instructor, by word of mouth, potentially with an interview beforehand - although I have disagreed with some of the interview questions proposed by a member of this forum.
If your OW course was completed well, I think there is no problem going straight into AOW, when conducted approriately. I think it should be looked on as an adjunct to the OW class, not some kind of almighty qualification. If you are concerned about buoyancy skills and diving ability, then for sure, getting a few dives under your belt before the AOW class is a good thing.
It is not strictly essential to be AOW or even rescue certified - I have dived with many people who had an OW cert from whatever agency, have hundreds of dives and are great in the water. However, personally, I think the "complete" Open Water diver, at least from my PADI perspective, is one whao has completed OW, AOW and Rescue. This is, after all, what other agencies teach by default.
If you think you are ready, whether you have 4 dives or 400, go for it.
Cheers,
C.