I know this is a somewhat old post I'm replying to, but I think this could be dangerous thinking. This is what gets people to think .22 WMR is a good SD round. Why? Because the gun is easy to conceal!
I live near Tucson, AZ. I wear T-Shirt and Shorts 9-10 months of the year (I'm in jeans and jacket mode at the moment). I have absolutely no problem concealing and carrying a Glock 19 and a spare mag comfortably. I understand, when we're talking 9mm, .40, .45, they're all almost equally bad stoppers. But I won't compromise below 9mm. It just took me 3 or 4 holsters before I found one that did what I needed it to. Too many people think that they can't conceal a big gun in T-Shirt and Shorts. I've concealed a Glock 21 in T-Shirt and Shorts. That's a big gun. Very few would ever call it summer concealable. I did it just to prove I could.
EDIT: Read the rest of the thread, and wanted to comment on this.
I'd choose the .45 each and every time. His skills with the Beretta will transfer to the .45. Maybe he's not as accurate, but in a life or death situation, being able to shoot lights out with their eyes closed (I assume on a square range, no pressure) will have little transfer-ability to a situation where people are moving around, adrenaline is pumping, etc. In other words, your friend will probably be almost equally bad at hitting his target in this situation with either gun. I'll take the round that makes the bigger hole.
Now, if it was a choice between nothing or the .22, I'd take the .22. But, repeat after me, ".22 LR is not a good defense round choice!"
In other words:
"Sometimes hollowpoints fail, so lets just load with an inferior round to match how the failed rounds act!"
The logic doesn't work here.