In a military sense, penetration is everything. Badguys wear armor, helmets, and hide behind logs and other cover. THAT is one of the primary reasons that militaries wise to stick with FMJ ammo.
This is less applicable in pistols, but it still applies. In a self-defense situation, you're probably not going to be shooting at someone hiding behind cover, or firing through a wall to get someone hiding on the other side. Soldiers do it all the time.
Also, I don't see why anyone assumes that a well designed hunting bullet can't be given a copper jacket and thus become FMJ. I mean, FMJ does not mean "round nosed". It means the bullet has a metal jacket. Nothing more, nothing less.
I've seen FMJ ammo deform mightily when firing through logs. South African .308 seems to separate the bulk of the bullet from the jacket and comes out all twisted in bent, when firing through a roughly 8" diameter log. Note though that a log provides much more resistance than a person's chest. Also note that the South African stuff is not really military FMJ, it's commercial, and is loaded more lightly than NATO spec. I'd really like to try a hot-loaded, 168 grain steel-cored bullet, but such things are illegal nowadays.
I don't like the way the poll is worded. I do think that JHP ammo is overrated, but that's not to say I think it's inferior to ball ammo and should be used less. It offers somewhat of an advantage when it works like it should, but the advantage is NOT great enough to say that FMJ ammo is useless as many seem to. Note that many, many people have been killed with FMJ, and yes, many of them were shot only once.
As I've said before, a larger or expanding bullet gives you a wider margin of error (that is to say, they might hit something that a smaller projectile might miss) but they're not going to make up for a grazing shot or a miss. They also (and this is important) will not make up for an under-powered cartridge. People here say that all handgun rounds suck that they're all underpowered. By that reasoning, more power can only be better, so long as it's not too much for you to comfortably shoot. Yet you hear people saying that such and such type loads are "too much" for self-defense purposes. It's only too much if the recoil/blast is so great that it affects your ability to shoot well.
You seem to get people that think of JHP ammo as a sort of death ray. I did a poll once, to see if not having JHP ammo would change your handgun choices. A LOT of 9mm fans said they'd stop carrying their wondernines. That, in my opinion, is flawed thinking. If you're not confident in the gun with FMJ ammo, then switching to JHP shouldn't in of itself change your mind, because while it can make a larger wound channel the difference is not so great that it'll turn a mousegun into a super-magnum.
In other words, if you can shoot well with a 9x19mm pistol, then carry a 9x19mm pistol, regardless of whether it's loaded with FMJ or JHP.
As for JHP ammo limiting "overpenetration"...blah. Police officers, statistically, miss their targets a lot more than they hit them, so the type of ammo they're using should be the least of their gun-related concerns. A missed shot flying downrange is more dangerous than a hit that goes through a badguy first.
