Police trade-ins are generally in great shape, have received periodic review and updates from the department's armorers, and generally have some extras, such as night sights or extra mags.
The down side is that they are often unusual models, like my S&W 4043 (which was my son's duty gun), with DAO triggers.
Carried a lot and shot little.
While police officers must qualify periodically, most officers probably don't shoot more than a couple of hundred rounds a year...(Most cops are NOT gun nuts; there are exceptions, but they ARE exceptions.)