Once again, we admit that neither system is perfect. The notice-and-takedown system is not perfect, and the notice-and-notice system is not perfect.
You're perfectly correct in saying that there are automated systems out there that are sending out notices under the notice and takedown. There are algorithms that are programmed to scour and search YouTube-type sites to automatically send out those notices—the DMCA notices, in the U.S. That happens.
If you craft a notice-and-takedown system, you can put checks and balances in place that prevent that type of abuse. They've talked about the fair use exceptions in the U.S., and a requirement for the intermediary to possibly consider those fair use exceptions in the U.S. before the takedown. That's one of the things they've looked at. That might not be the best solution, but you could put some checks and balances in place.
The end of the line—the overall answer—is that the notice-and-takedown system is more effective than the notice-and-notice system.