These are actually two different products with different rolls and options.
If you are looking for a simple point to point connection with the capability of streaming data at up to 80kbps, you must use the XBee 802.15.4 modules.
If you are looking for a network where you can have a Mesh network where some nodes are acting a repeater or routers to get data to nodes that are out of range, then you want the XBee S2C ZB product.
Can you make the S2C function as a Point to point connection, you can. Just configure one as a Coordinator (CE1) and then set the addressing of both are pointed to each other.