Dr. D, from my perspective, your question is rather like asking if one really needs a good fire extinguisher or a good insurance company. You and I would probably agree that we want a dependable fire extinguisher that will put out the fires we would most likely experience in our situation, and we want insurance companies that can perform when we have a claim.
I don't expect to ever use a firearm in self defense, but that would be my most critical use for any of these tools. If that occasion ever occurs, I want to be able to shoot with precision, the firearm must not jam or malfunction, and the ammunition should give me the best chance of quickly stopping the problem. I'm willing to pay a bit extra for good quality self defense ammunition, as long as it really makes some difference. And, then we get into the 'scientific' studies, arguments and so on.
I'm a neophyte regarding most of these arguments, but it is logical to me that I should care about the reality of different ammo.
Now if you are really questioning whether anyone ever uses a firearm for defense, then I would respectfully suggest you check the research of Dr. John Lott and Dr. Gary Kleck for starters. Numbers are all over the board (including various threads on TFL), and estimates run from 500K to 2.5mm times per year for civilian use of firearms in self defense. In most of those cases the weapon is never fired. In cases where firearms have been fired, there are various studies of the results. And, clearly LEO's provide plenty of examples where people need to use firearms against BG's.
If you examine the Firearms Tactical site I think you'll also notice a professional association called the International Wound Ballistics Association -
http://www.iwba.com/ . Sounds macabre, but there is certainly a legitimate need to logically understand what various firearms and ammunition can accomplish during legal and moral use - such as enforcing law and defending life against coercion.
Sorry ... long-winded as usual.
Regards from AZ.
[This message has been edited by Jeff Thomas (edited July 28, 1999).]