I'm not defending things one way or the other, but trying to post up some (I believe to be) sensible, factual information I was told by my CPL instructor:
The main reason you do NOT carry handloads in your gun is not reliability, and it's got nothing to do with the "rightness" of a justifiable self-defense shooting.
The main reason is forensics. If you're carrying handloads in your 9mm, and you get attacked and kill a guy in justifiable self defense, you should be exonerated of any wrongdoing if it was justified. Shootings, even justifiable ones, don't happen according to a script though and in many places (including here in MI) you have an obligation first to flee/etc to avoid a shooting as anything but a LAST resort. So it matters whether a guy was 6 feet from you or 40 feet from you in many instances. It matters if he was facing you or shot in the back. So on and so forth. The guy you shot's family, whether he was a %&*#&* or not, is going to be out for blood in many cases.
With FACTORY ammo, you have the forensic benefit of a selection of ammo from a certain lot number. More of that ammo can be purchased by investigators and tested - for things like how far a given load's powder spreads (determines distance in close-range situations) for powder residue on the parties involved. Investigators cannot take "your handloads" and say with any provable certainty that at 5 feet this load leaves this much GSR, or stippling around a wound, etc. They're taking your word for what was in the actual rounds fired.
And all that is to say nothing about the shooter being wrong, right, or whatever - factory ammo just furthers the ability for forensic proof to be had because it's reliably re-produceable.
Do I carry factory ammo? You bet. Do I think that shooting someone with handloads in justifiable self-defense "WILL" get you in trouble? Not necessarily - I'd hope not.
But when stuff hits the fan and people are throwing mud against the wall to see what sticks, I'd like to keep my wall as greasy as possible! The way I see it, IF there is ANY chance I'll have some additional forensic advantage in order to prove a good shooting by carrying factory, I'm doing it. I would never dog someone else for carrying handloads so don't misread me - but I do think they're at a legal disadvantage to someone who does, regardless of how small that disadvantage is.
Just my 4 cents.