Centralized mode puts Cisco AireOS-based wireless controller functionality in an appliance onsite or in a data center. It supports up to maximum access points as per model, and licensing is required. Mobility Express also uses AireOS-based controller functions, supporting up to 25 access points per instance with no license required.
There are several differentiators:
● Simplicity, including default “best practices” settings ported from 10+ years of large- and medium-scale implementation experience
● Advanced radio resource management capabilities
● An advanced smartphone application, called Cisco Wireless, with easy-to-use dashboard views and drill-down capabilities
● Mobility Express is the value leader for gigabit Wi-Fi and 802.11ac Wave 2 multiuser multiple-input multiple-output (MU-MIMO) capabilities.
http://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/mobility-express/q-and-a-c67-734485.html#_Toc428483994
