You need prsysmgmtui to check the system configuration and the components health. For example you can check the runtime env for the node or check if the system or custom agents are running properly or not. EC2 command line tool is for dev ops work to monitor and configure the infrastructure for the server or instance. So, both of these are used for different purpose. Prsysmgmt is to manage the product level components and ec2 is for infrastructure level management.