.410 rifled slugs leave a lot to be desired. You will be better off starting a child on something that gives them a good chance of success. Buy a .243, potent and with almost no felt recoil and can be used for the childs whole life. I have never fired a .44 mag from a rifle so I don't know what the recoil is like, I suspect not bad and I will kill a deer and if you are limited to those two choices, I would go with the .44. I am asuming you are not planing to use a .44 mag bullet in a .410 shotgun, that would not be a good idea.