* Which model is more likely to prevent someone with mental illness from harming himself or others because of incorrect diagnosis?
* Which model is more likely to lead to scientifically sound treatments for his malady?
* Which model is more likely to encourage people to generally think rationally about the real world around us?
If you give 40,000 people a random mix of placebo and vaccines and then monitor whether or not they contract the target disease, you get an indication of efficacy by comparing the vaccinated group to the placebo group.