Wireless: Support 5GHz in all access points
All Sophos AP's need 5GHz connectivity. All professional wireless devices (Notebooks, mobiles ore whatever) are able to connect via 2,4 and 5GHz.
5GHz technology is more stable as 2,4 GHz and has numerous advantages.
2,4 is not really more stable than 5 Ghz, because you are loosing range with 5 Ghz. In an Office with 2,4 Ghz WLAN you need more 5 GHZ Access Points to caver whole Office.