The A320NEO (New Engine Option) as its name suggests represents a major development of the successful A320 series built primarily around the provision of a new powerplant. Though there are other improvements, externally it is only the new engines that define the type. Since 2012 even the NEOs large Sharklets on the wings have been applied to the existing model of A320 in new constructions and retrofits.
China Southern A320neos. a380.boards.net
AerCap Leases Twenty-Four A320neos to China Southern, Asia's Largest Airline. Aercap
First A320neo for China Southern Takes to the Skies. China Aviation Daily
China Southern to Take Delivery of First A320neo in Mid-December. China Aviation Daily