The majority of agencies in this area use Win RA9T and have had outstanding success with it in numerous OIS incidents in barrels from 3.5" to 5" lengths.

Keeping in mind that all service caliber handguns in general offer relatively poor incapacitation potential, any of the following loads will work adequately in 9 mm:

Barnes XPB 105 & 115 gr JHP (copper bullet)
Federal Tactical 124 gr JHP (LE9T1)
Speer Gold Dot 124 gr +P JHP
Winchester Ranger-T 124 gr +P JHP (RA9124TP)
Winchester Partition Gold 124 gr JHP (RA91P)
Winchester Ranger-T 127 gr +P+ JHP (RA9TA)
Federal Tactical 135 gr +P JHP (LE9T5)
Federal HST 147 gr JHP (P9HST2)
Remington Golden Saber 147 gr JHP (GS9MMC)
Speer Gold Dot 147 gr JHP
Winchester Ranger-T 147 gr JHP (RA9T)
Winchester 147 gr bonded JHP (RA9B/Q4364)

While bullet construction is a significant factor, a gross generalization would be that faster loads tend to work a bit better against metal intermediate barriers, while the heavier loads tend to work a bit better against glass intermediate barriers.

Pick the load that you shoot most accurately, that is most reliable in the type of pistol you choose, that best suits you likely engagement scenarios, and that you can acquire in sufficient quantity (at least 1000 rounds) to assure initial function along with periodic re-assessments.

Whatever you choose, make sure you fire at least 500 and preferably 1000 failure free shots through your pistol prior to using it for duty. If your pistol cannot fire at least 1000 consecutive shots without a malfunction, something is wrong and it is not suitable for duty/self-defense use.

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The keys are:

-- Cultivate a warrior mindset
-- Invest in competent, thorough initial training and then maintain skills with regular ongoing practice
-- Acquire a reliable and durable weapon system
-- Purchase a consistent, robust performing duty/self-defense load in sufficient quantities (at least 1000 rounds) then STOP worrying about the nuances of handgun ammunition terminal performance.