For folks familiar with Exchange 2010, there are 3 ways to manage Exchange: the Exchange Management Console (EMC), the Exchange Control Panel (ECP), and the Exchange Management Shell (EMS).
As far as the GUI-based experience is concerned, customers are faced with an incongruous choice between EMC and ECP. While most of the management surface is exposed via EMC, some newer features such as Auditing, eDiscovery, RBAC management, Group naming policy, ActiveSync Quarantined Device management, etc., are only available in ECP. Since these features are applicable to both on-premises as well as online deployments, administrators are forced to learn multiple tools and juggle between them. Specifically for the MMC-based EMC, customers also have to bear IT overhead with respect to updates, patches and so on.