I personally believe spanking, if done on a rare occasion, accomplishes way more than a parent who hits a child all the time.
You are smart. You first think of the kind of person you want to “grow” from your treatment of the child, and plan accordingly. Rough, insensitive treatment breeds ugly people and we all know too many bastards in this world.
But cautious spankings of preschoolers can be defended to them later as an adult: I spanked you on the tush when you put my glasses in the toilet; when you ran toward the street, when you spit on your playmate - etc.
I am fond of the idea that when the kids reach adulthood, they can remember specific spankings. That sounds odd but let me explain: I know one woman who was beaten all the time as a child. We were talking about her childhood and I asked her, “Why were you beaten?” She couldn’t remember many misbehaviors... they all sort of blended together because she was hit so many times. What she can remember is when the belt buckle drew blood on the back of her legs, when she had a hunk of hair ripped from her scalp that left a bald spot and when she was kicked down the basement flight of steps. THOSE behaviors she remembered only because the punishment was a bit more severe than the others. What I hope to achieve is my son saying, “I got a whack on the butt when I ran into the street” or my daughter, “I got a whack on the butt when I climbed on top of the table” (that is a long story but she deserved that one).