What is meant by "its wide variety of defensive countermeasures at the ready?" This seems to suggest it has more or different countermeasures than other ships, is this the case?
Cloud Imperium
This indicates that the Prowler has the full range of countermeasure types: flares, chaff and decoys. Many ships have only one or sometimes two of these at a time.
starfarer.space · Q&A: Esperia Prowler - Part II