The .32 ACP belongs to the class of what I call the "eye, ear, nose, and throat" guns... because those are your preferred aiming points.
Seriously, the .32 ACP earned its anemic reputation as a poor self-defense round because shooting someone with ball ammo is akin to stabbing them with a Phillips head screwdriver. It hurts, it very well may kill them... eventually, but it isn't going to stop them unless you stab them in the right place. Buying ball ammo is an attempt to turn a sow's ear into a silk purse... and it ain't gonna work. Use Winchester Silvertips instead... they do expand because the lighter bullet goes fast enough, and they penetrate enough to let the expansion actually do some good.
If you're bound and determined to carry ball in this caliber because you want penetration, you're fooling yourself and you're probably going to end up dead if you are forced to resort to using your gun and ammo in a defensive situation. If you really need penetration, because of winter and people are wearing thick clothes, etc., then choose another caliber... like the 9mm.
There are two components to "stopping power", the physical and the psychological. Physical stopping power (absolute stopping power) is caused by turning the brain off by destroying enough vital tissue that the attacker can no longer function. Hit someone in the brain, the aorta, the carotid artery or jugular vein, the spinal column, or some other area where even a relatively minor injury will cause an immediately life-threatening or -ending injury, and they're going to be stopped.
Psychological stopping power is the more uncertain of the two, and it occurs when the person who's attacking you becomes more worried about their own survival than in continuing the attack against you... whether or not your hit was life-threatening or whether or not you even have to shoot (that's why pointing a gun at the bad guy discourages many of them). For instance, hit someone in the shin with a bullet and it's going to HURT. Shoot them in the jaw and shoot out a few teeth on the way in, and it's going to HURT. Of course, for pyschological stopping power to have an effect, the person you have shot must have the mental wherewithal to realize that he has indeed been shot and to consider the effect on himself.
I have talked to police officers who are dealing with people on crystal meth, or PCP, on a regular basis. People under the influence of these drugs can become fairly numb to pain, and can also be in a psychotic state where reality won't intrude. My LE friends have told me of being attacked by a naked PCP freak (seems a recurrent theme is for PCP addicts to end up naked because the drug makes them think they're really hot... even in the winter), and breaking this person's arm with a restraining hold yet the attacker still kept trying to attack because he felt no pain and didn't realize his arm was broken. That's when you see a bunch of cops clubbing an attacker with their batons, pepper-spraying them (they don't feel pain, but swollen membranes make it hard for them to breathe), etc. Shades of Rodney King (who I believe was "dusted").
If you are attacked by someone on PCP, or crystal meth, or some other substance that deadens pain and reduces the user to an animal, raging state once the adrenaline starts flowing, then chances are you are going to have to physically destroy enough of their body to eliminate their capability to continue the attack because they aren't going to respond to psychological stopping power. These criminals are the reason we have .223s and 12ga shotguns loaded with double-ought buck. Like the Moro juramentados in the Phillipines who withstood multiple hits from the .38 Special and kept on coming (some of those guys were shot repeatedly with Krags and kept on coming), and like a charging grizzly, you're going to have to shoot for bone and break them down.
The .32 ACP is really too anemic to be a primary self-defense handgun. I know, they're nice to carry (I have a Seecamp), but they're really the gun you carry when you can't carry anything bigger... and you need to realize you are basically shooting a .32 drill. My strategy when I'm carrying the .32 has always been to load it with Silvertips, act like a complete wuss if someone confronts me with a deadly weapon, sucker them into complacency, and then ambush them as I go to draw my 'wallet' and empty the gun into their upper chest and neck... and then run like hell.
Quite frankly, a S&W Airlight weighs less than a Seecamp or Guardian (and not much more than a P32), hits a LOT harder, penetrates a LOT better, is more reliable than ANY semiautomatic, isn't that much harder to conceal... can you see why I seldom carry my Seecamp anymore? Also, despite the rudimentary sights, I have no problem keeping them all on a B27 or IPSC target at 25 yards, and head shots within 10 yards rapid fire are also easy (all it takes is proper instruction and practice).
