Personally. .380 or better to open, with hand loads, however as of late there are some pretty good commercial rounds now being loaded for it..
Now, if I got my hands in the right .32 revolver, in 32H&R mag or .327 Max.. with some load development that could prove to be a winner..
22lr would defiantly work, with the right ammo and barrel length,, There have been more fatalities recorded with the 22lr than all other rounds.. Not my 1st choice, but depending upon how I had to dress, the occasion.. it could have a place..
The 25acp, no way, I have seen the post shooting reports where suspects took multiple rounds from 25 acp's and shook them off and kept coming.. one in the bridge of the nose and it ringed and popped out his forehead!! It never penetrated the skull... Real Deal... The bad guy continued his assault on a Undercover Officer on a buy-bust, fortunately there was a uniform back up that put him down with a 44..