Does anybody really know the answer to this? I mean, I could go on about the wonders of Hydrashock or Golden Sabres, and others can talk about different brands. But do we really know what the hell we are talking about? To me, I have gotten a bit cynical about the whole thing. I'm thinking that if its a jacketed hollow point that feeds reliably and goes bang every time, I'm not sure that there is much of a difference. Am I wrong here?
FQ13 who doesn't want to be carry trash, but I'm not really sure how one quality brand is that much better than the other as long as your pistol likes it. 
You could be wrong.
Expansion and penetration is what is required to maximize your chances of stopping the fight, and not having the other guy stop it for you.
The latest improvements in bullet design have allowed the 9mm to approach the performance of larger caliber rounds. However, reliable expansion and penetration are more important to it's success than in the larger calibers.
A hollow point that does not reliably expand and penetrate after passing through a layer or two of clothing leaves you will 9mm ball ammo, which shouldn't be anyone's choice for a self defense round.
In repeated tests using ballistic gelatin and passing through various media before entering the gelatin block, Corbon DPX is found to be the top performer. Whether the difference is worth the price, I can't say for you, but when my life is on the line, I'll take any small advantage I can get.
The current wisdom calls for 12 inches of penetration after passing through some type of clothing as being ideal. Expansion while maintaining the maximum penetration up to 12 inches is desired. And while 12 inches seems a lot, this is in pure gelatin, not a body with bone or other obstructions which will reduce actual penetration.
Penetration over 12 inches is viewed as non-desirable as it will increase the probability of the bullet passing through the target, causing collateral damage.