as I always try and tell folks buying handguns, the GUN that fits the shooters hands , they will always shoot better than a gun that YOU think is a better gun!
SO this being said, I would take the kid to a few shops and let HIM hold a few and see what one HE likes best and best fits HIM

as for the two you listed above, the mark IV Competition model would get my vote of them two listed, if it again fit the kids hand well

also note there was a few recalls on these mark IV pistols, so if buying one ask if the recall was done or not on it!