The slide below explains the differences between the two antennas:
Basically, ENSTATION5-AC has Wave 2.0 protocol in WiFi 802.11 ac standard, which optimizes the usage of simultaneous channels, communication distances and speed.
In addition, the ENSTATION5-AC's PoE protocol is a proprietary one, while ENSTATIONAC's PoE protocol is standard and therefore easier to interface with other manufacturers' devices.