Because RMS is primarily an agentless data collection tool, the deployment is easy. You need not distribute software to every computer from which you collect data. Instead, you deploy components on a limited number of computers that in turn collect data from the targets. Since you only deploy a limited number of components, upgrades and maintenance tasks are simplified.
On the other hand, the agent-based approach can be useful in specific scenarios. In particular, communications with computers located in a firewall DMZ are simpler with agents than with an agentless approach. Also, agentless data collection means that a great deal of asset data is transmitted to the computer that collects the data. With the agent-based approach, only results are transmitted, not the actual asset data.