The debate between Agent based and Agentless monitoring is one that has been happening for long in the network management industry. However, most companies prefer Agentless performance monitoring since it takes the upper hand through the following advantages:
Agentless network monitoring is a technique in which the monitoring server directly polls the devices in the network periodically to monitor their health and performance.

This method is more reliable and efficient when compared to agent based monitoring in which the data required for monitoring the health and performance of the network devices is collected by agents and transferred to the network monitoring tool
Unlike agent-based network monitoring, agentless monitoring monitors the assets in the network with the help of protocols which are already installed in the devices and application to collect the required data. These protocols, commonly are WMI, SNMP, NetFlow which basically are device dependent. The devices in the network are just configured to communicate and exchange information with agentless network monitoring tool.
One of the main reasons to choose agentless network monitoring over agent-based monitoring is to save time and effort, which in turn cuts down cost. This type of monitoring is best for beginners as it lowers ownership compared to agent-based monitoring. Also, it is highly suitable for centralized network with limited resources. Agentless network monitoring is of great help to small organizations without the need to install agents for every set of devices. Hence, they are less intrusive with more flexibility than agent-based network monitoring.