Spoon,
I see that you are not getting any answers to your question, so I'll take a shot at it.
As you have noted in other posts, it is always the instructor who makes the course into something valuable to the student.
I am both a PADI IDC Staff Instructor, and an IANTD Instructor Trainer, so I know both courses.
They are both good courses, and are a lot of fun as well. It is hard work, but doing the rescue scenarios is very enjoyable, if they are well "acted".
If I had to rate the two courses, I would have to describe the IANTD course as more demanding, but again, it is always up to the instructor. Either one will help make the student into a better, more self-reliant diver.