If you plan on using a revolver for self defense (SD), than a 22lr revolver makes sense. I would buy a gun that closely matches your SD revolver (e.g. get a ruger SP101 if you plan on carrying a ruger for SD).
Re: the SP101's double action trigger is terrible. However, you could have a good gunsmith perform a trigger job on it. Typically, rimfire revolvers need heavier springs to consistently ignite the primer, so you may never quite match what your SD revolver's trigger feels like.
Personally, I use an automatic for SD, and have a 22lr upper that I put on it to save money on training. It's not quite the same thing, but it is very close.
22 revolvers are awful fun; I've had many, and still have six of them in my safe. I got a lead on a S&W model 18 for $475 this week and had to talk myself out of driving 100 miles to check it out.