Hi PK

One of the Major Advantage Of Using ACC Over Horizontal Discovery is Security - Why 

ACC is agent based discovery where ACC do not have to Pick the Credentials at Run time rather ACC Agents keep sending data to Mid Servers. 

Horizontal Discovery - We create Credentials (Windows , SSH , SNMP ) for Discovery . These Domain, Root credentials are stored in Service Now Credentials table which is on Service Now Cloud. Security Experts see it as a very big risk . Even in Horizontal Discovery Password Vaults Like Cyber Ark can be used but seems in yoor case customer is more happy with ACC.

Capability wise Horizontal Discovery Is More Powerful.

Regards

RP