But at any rate, you counting on a bullet to stop a threat is bad medicine. You are much better off to become proficient at hitting your intended target rather than hoping a big fat bullet will do it for you.
Everything Bama Mike said is true, .45 ACP has about the least velocity of all handgun rounds. It's actually slow enough that if you stand at the right angle from the shooter and the light is just right sometimes you can see the bullet in flight. .45 ACP generally leaves the muzzle at around 850fps, which is subsonic. 9mm leaves the muzzle around 1100 to 1200fps, which is supersonic.
Like Bama said, relying on a big fat bullet as opposed to good shot placement is faulty strategy. You are talking about a difference of less than 1/100th of an inch (.355" vs .451") in diameter between bullets. There is not a hill of beans difference in hitting someone with a .45 versus a 9mm. Unless the hill of beans in question is .096 inches tall
And like I said earlier, Law Enforcement Officers are not necessarily firearms experts by default, I work with a bunch of them. My co workers come to me for advice for their backup or off duty carry guns. Not that I'm a genius by any means but they know I've done my research.
If you want home defense firearm and don't want to worry (too much) about shot placement then you need a 12ga shotgun. Long guns are easier to make hits with than handguns. No shotguns don't fill an entire hallway with lead like the movies but if you place the bead somewhere on the torso at 0-15 yards and squeeze the trigger you will likely put lead in a vital organ, assuming you are using buckshot.
Don't buy a .45 just because someone has sold you on all the old .45 myths, handgun "stopping power" is a myth and nothing more. Shot placement with a round that can penetrate deep enough to reach vital organs is the only "stopping power" in regards to handguns. I don't hate .45, I actually love it (don't get me started on .40SW) but any time a new shooter asks me what they should get I recommend a larger pistol chambered in 9mm like the Glock 17, 19, Smith and Wesson MP9, or (my favorite) the CZ75. This is for the simple fact that 9mm is perfectly adequate for self defense while still providing minimal recoil and cost to practice.
The last two people I recommended handguns for were my parents, my mother listened to my advice and got a Glock 19 9mm, my father didn't and got a lightweight Kimber 1911 in .45... Guess which one wants a new handgun now?