Either one will kill a person, and both are a poor choice for the job.
The .25 has a slight edge in a vest pocket pistol, all other things being equal, but is that edge beyond the point of "just noticeable difference" in terms of effectiveness for self defense. Don't know. The edge is slight, and I suspect the edge is not great enough to make a difference. In terms of reliably operating a semi auto small pistol, the .25 acp is a better choice, assuming it is a quality pistol, most are not anyway.
Locally, a guy, an abusive estranged husband with a protection order, shot the wife with a .25 acp and then himself just a couple of days ago. She took several rounds at point blank range to the head and died at the hospital. He shot himself in the head, was transported to the hospital, and is now improved in condition. He is expected to make a good recovery. t is not yet known if his intellectual functioning will be at the same low and ineffective level it was prior to the gunshot.
"A Liberal is someone who doesn't care what you do, as long as it's mandatory". - Charles Krauthammer