Hi Milind,
Below is the basic difference between APC & Ariba P2P
APC
Ariba Procurement Content supports multiple approaches to managing and accessing catalog content. Authorized users can load, manage, and access catalogs and prices stored in the solution. It supports catalogs in CIF and cXML formats and allows loading of catalogs from Ariba Network
Ariba P2P
Ariba Procure-to-Pay supports end-user requisitioning and requisition approval for use in monitoring and compliance. Ariba Procure-to-Pay generates purchase orders (POs) from fully approved requisitions.Purchase orders can be delivered to suppliers through Ariba Network, which supports a number of delivery formats, including fax, email, cXML, EDI, and manual delivery. Suppliers can only return order confirmations and advanced ship notices through Ariba Network. Ariba Procure-to-Pay supports invoice management, reconciliation, and approval.
Cheers!!
Aditya