Pro's and con's ... if your time is limited and you're only planning to dive under supervision, nine dives worth of training is better than four dives worth. On the other hand, if you're struggling with basic comfort, awareness, and buoyancy control, you're not likely going to get anything out of AOW ... and you certainly won't come out of it even remotely qualified to plan and execute a deep dive without supervision. Sadly, having access to deep dives is exactly why most folks take AOW.
I personally won't allow my students to go directly from OW to AOW ... not if they want the latter class from me. I want them to gain some experience, get comfortable with OW-level skills, and develop a little bit of confidence in their underwater ability first. That way they can focus on learning new things, rather than using the class to simply reinforce what they were supposed to have already learned. Then again, I don't train divers to follow dive guides and rely on someone else to make all their decisions for them. I won't take a diver deep until I'm confident that their buoyancy control won't result in an accidental ascent, and their awareness level is at least adequate to keep track of their depth, time, NDL and remaining gas ... and that's the bare-bones minimum starting point. I won't train complex navigation until they can look at their compass without losing buoyancy control, or need to settle on their knees first.
To be fair, there's only so much the typical student can learn in four or five OW dives (depending on agency) ... after that, they should get out and practice. My rule of thumb is get completely comfortable with what you learned in the last class before considering signing up for the next one. That way you can concentrate on the new stuff, rather than the things you should already have "mastered" ...
... Bob (Grateful Diver)
Bob, could not have put it better myself, exactly the way I train and recommend to my students.
As for the deep dive training on AOW, well I put an awful lot into the "Deep" dive briefing, OK not all of my students are going to be able to come out at "expert" level but they do go away with an understanding of gas management, redundant air supplies, proper dive planning and enough knowledge to know that jumping off the boat and going to 100 ft without proper planning is going to get them into trouble.
I also do the deep dive as the last dive of the course, by then we have much more confidence, buoyancy issues have been solved, any remedial training (from OW) has been done and they have already gained a lot of knowledge and some experience.