Part II: Exchange 2016 vs Exchange 2013: What is the difference?

• Server role consolidation
  In previous versions of Exchange, we had option to install the Client Access server role and the Mailbox server role on separate computers. In Exchange 2016, the Client Access server role is installed as part of the Mailbox server role. Client Access server role is not available as a separate installation option.
  A multi-role Exchange server architecture benefits:
  • Simplified hardware purchasing, maintenance and management of the Exchange servers.
  • Fewer physical Exchange servers resulting in less maintenance costs, less Exchange server licenses, and less rack/floor space, and power requirements.
  • Improved scalability. During a failure, the load on the remaining Exchange multi-role servers increases only incrementally, hence no adverse effect on other exchange functions.
  • Improved resiliency, because a multi-role Exchange server can survive a greater number of Client Access service failures.
• Search improvements   The local search instance is now can read data from the local mailbox database copy. Hence, no need for passive instances to perform indexing from their Active counterparts.
• Office Online Server Preview for Outlook on the web document preview
  In Exchange 2016, Outlook on the web uses Office Online Server Preview to provide rich preview and editing capabilities for documents. You need to deploy Office Online Server Preview in your on-premises environment if you don’t already have it.
• MAPI over HTTP is the default for Outlook connections
  In Exchange 2016, MAPI over HTTP is enabled by default, and offers additional controls, such as the ability to enable or disable MAPI over HTTP per user, and whether to publish it to external clients.

Read more about Exchange 2016 architecture in Part I: Exchange 2016 architecture.