Case-Control or Cohort?

Both cohort and case-control study designs have their place in providing epidemiological data to develop health policies.

Which design would you use to provide data that can be used to establish health policies with respect to chronic diseases such as diabetes, heart diseases, or cancer? Why would you use that type of study design? Do some research online for an example where a cohort or case-control study has been useful in understanding the health or economic impact of a disease or a risk factor in a community.