I always use snap traps. You never know where that mouse is gonna be when it dies, and the smell is horrid.
That is the only kind we use. After one smelling seemed like a month under the house, never used poison again. My cat used to bring rats to me, he would pass right by Jake and give it to me. Same thing with squirrels and chipmunk's, only most of them were alive. We named one Girlie, and it would climb all over us, liked Jakes pocket. So did chipmonk.
. And the letters the " kids" write are really from adults, majority of the worlds starving children can't read or write nor are the able. Most of that money goes to the fund raisers. Like the American Red Cross, once I read that Liz Dole was paid millions for her job, we never donated another dime to them. Seems nothing is as it seems.
I'd think the odds of you causing it more misery are few, saving a cat or dog from certain death and misery are few in comparison. Not to speak of how much joy it brings to you and the animal. Of course they can be 'trying' at times, still my little Foxy has become my "therapy dog" I've wished a hundred times I didn't give our feral kitten, Sheba away. She was so cute and Foxy and her loved each other instantly.