I'm not trying to stir the pot here, I'm just legitimately curious... Folks around here are adamant that the bare minimum for a dependable, battle-ready rifle/carbine is a Colt 6920, which don't get me wrong, makes perfect sense considering that it's basically just a semiauto/16" bbl variant of the M4A1, but there are an awful lot of Law Enforcement Agencies equipped with various models of Smith & Wesson M&P15.

To the best of my knowledge, no model in the M&P15 Series of rifles/carbines has ever been built to the same specifications as the Colt 6920, much less have they ever been built to higher specifications. So if the Colt 6920 is the bare minimum for a hard-use, duty-grade AR Pattern weapon, then how do so many PDs get away with equipping their sworn officers with an objectively inferior weapon?

Honestly, do they just get such crazy good deals on them that they can afford to purchase replacement parts of higher quality on the side and upgrade them accordingly? Do they rely on S&W's Warranty to replace any broken parts as they occur? Do they simply not fire enough rounds in training within their average service life for it to be an issue?

Enlighten me.