I don't think the choice is between certs and experience, far too much relies on the individual diver.
I haven't made that many dives, but already I've noticed that there is NOTHING I am going to learn by diving with and watching many other divers. While I'm capable of practicing technic solo, I often find it better to dive with someone with much more experience. Small things, such as how they hold their hands, clip lights, use different kicks in different situations adds to the learning experience.
Often a certification allows one to dive with an experience diver and concentrate on learning these skills. If you are lucky enough to have many skilled divers to dive with, then I'd think advanced certifications would be less beneficial.
I just got my Night certification, they were great dives. I feel I learned far more by having one on one instruction and diving with a very experienced night diver, than I would diving with a group, and a DM who had to be swimming around checking on everyone.
Even if group lead dives, the DM often dive differently than they do when diving with and responsible for just one buddy. I sort of view the advanced C cards as paying someone to dive with me, so I can learn from them. With luck, I could learn the same for free, but I value people's time, and I'm far more likely to ask questions and learn when I'm not as concerned with my buddy having a good time. Not that I don't want instructors to have a good time, but if I'm not paying someone, both should have equal fun. As a student, I expect the scales to be tipped in my fun and learning favor.
Xanthro