Software as a Service (SaaS) offers the least amount of security responsibility for the end-user or organization, as the service provider manages the underlying infrastructure, software maintenance, security patching, and updates. Choosing a SaaS application means the colleague's organization would not be responsible for the physical servers, operating systems, or the application's security configurations, making it the best option for minimizing their security responsibilities.
References:In the Certified Incident Handler (CREST CPTIA) course materials, the various cloud service models (IaaS, PaaS, SaaS) are discussed with a focus on their implications for security responsibilities and management.