At first sight, both the solutions seem quite similar; however, there is a clear difference in that one is a passive monitoring and detection system that limits itself to raising an alarm at an anomaly or signature match, and the other is an active prevention system that takes proactive action when detecting a malicious packet by dropping it.
Usually, a NIPS is inline (between the firewall and rest of the network) and takes proactive action based on the set of rules provided to it. In the case of a NIDS, the device/computer is usually not inline but may get mirrored traffic from a network tap or mirrored port.
The network overhead in the case of a NIPS is more than that of a NIDS.
Another issue with a NIDS is ...