The question was asked, "Which is worse, spanking my child or yelling at them?"
It was interesting because the person asking the question was basically saying, "Yes I know that both are not good, but I am going to be doing one of them so please give me something I can do that will not be as bad as if I did the other one."
My answer: Both are not good and I will not give you permission to hit or yell. There are times when each might be an effective strategy, but the problem comes when anything is overused. I tell parents that they can spank their child three times. Not three swats as one person wanted. "You mean I can hit them anytime I want as long as I limit it to three hits?" I mean save it for the big things and you will be surprised how creative you can be when you don't want to waste one of those times.
Now the problem with yelling is that itto sets a model for what is acceptable. If you yell then you will have your child learn to yell back at you, at their friends & siblings, at the pet, and at grandma and grandpa if they get upset. So neither strategy is really effective for the long run.