IaaS pros: You have full control over the system and infrastructure.
IaaS cons: You need to have system administration expertise to maintain the security and reliability of your system.
PaaS pros: You can focus on developing cloud apps while the responsibility for the system’s management is taken by a cloud provider.
PaaS cons: Your engineers have limited access to certain aspects of the system like packages and their versions.
SaaS pros: You get rid of the headache associated with building and maintaining the app as it is delegated to the vendor of your choice.
SaaS cons: You may have limited control over the internal processes and workflows.