I won't get into which one I believe is "wrong" per se, but I want to go into why corporal punishment can be less effective than strict non-corporal punishment.
Here is an example to help guide the distinction between the two:
Next Friday, Billy does the dishes out of apprehension of being smacked. He learns not to do certain things through corporal punishment effectively, as long as their is a consequence of physical punishment whether it is mild to severe.
Billy is now 20. He works in a paper mill. His employer tells him that he needs to do task A, B, and C every night before he leaves the mill. Billy knows that his employer will not smack him as a punishment, therefore, he does A and B, but not C.
Corporal punishment only works when their is apprehension of physical punishment. Period.
A counter claim to this would be, " well, my parents only spanked me as a punishment, and I adhere to rules in college and work, therefore corporal punishment does teach a child to be adherent to authority figures. "
I'd like to note that most parents that use corporal punishment do also utilize other forms of punishment.
Well, even parents who only use corporal punishment do send kids to school, extracurricular activities, other family members who don't use corporal punishment, along with many other institutions and situations that call for other forms of discipline. So, although your parents did use corporal punishment, you most likely have learned other forms of discipline that readied you for adherence of authority figures without the use of apprehension of physical harm.
Now, let me give an explanation of strict non-corporal discipline:
Next Friday, Billy does the dishes out of apprehension that his rewards and possessions will be detracted from. As long as their is apprehension of losing rewards or possessions, he will adhere to authority figures.
Billy is now 20. He works in a paper mill. His employer tells him that he needs to do task A, B, and C every night before he leaves the mill. Billy knows that his employer will not smack him as a punishment, but will in fact take cut his hours, take legal action, and/or take away his job. Since Billy has been equipped and conditioned with the idea this type of punishment, he is more likely to adhere to the authority figure.
Let me also remind you of the various studies done by the American Psychological Association among other nationally/internationally recognized groups, there findings, to be summed up in a sentence would be, corporal punishment causes a child be more likely to have violent tendencies, abuse their own children, not adhere to authority figures, among other negative effects; these effect are more prevalent or severe in depending on the amount of force used by the parent.