Isn't is amazing how many people will tell you about their semi autos when you ask a question in The Revolver Forum??
I don't carry a .22 because I am still physically capable of handling larger calibers which are (presumably) more likely to be effective. However, ANY gun when you need a gun is better than no gun.
Where the .25acp shines over the .22LR is feeding in semi autos. Not a concern for revolver users.
Where every centerfire has the advantage is ignition. Rimfire rounds are more prone to not firing then centerfire rounds. Even "quality" .22LR sometimes has a round that doesn't go off as planned. Various batches of budget stuff is notorious for that.
The reason is the way the cases are primed. A drop of the priming compound (as a liquid) is put in the case and then it is spun to distribute it inside the hollow case rim. Once in a while a spot gets "missed" and once in a while that missed spot is what is under your firing pin. Very often a .22LR that doesn't fire, will fire if replaced in the chamber so a different part of the rim is struck by the firing pin.
SO, as long as you are ok with that possibility, the .22 RF is ok for defense, and can be superior to a .25 or .32 with a FMJ bullet (or a JHP that doesn't open up), the lead bullet of the rimfire can be as or more effective, sometimes.
.22 Mag is a better choice, for a defensive round, but still has the possible issues of rimfire ignition.
A .22 you can handle is better than something else that you can't. ITs that simple.
better if you can handle something bigger, but life is what it is, and we live with what we can do. My mind still thinks I'm 25, but my eyes, and the rest of me constantly tell me I'm 40 some years past where my mind is still stuck.