As a penetration tester and security consultant, you have been engaged by a company to assist them in selecting an Intrusion Detection System (IDS) for their infrastructure. They're considering installing a signature or anomaly based IDS product. They've asked you to provide a concise analysis of the strengths and potential weaknesses of each of the IDS types.

Discuss and explain the strengths and weaknesses of each type of IDS and any considerations they should make in selecting one over the other.