What P0ker and IONIC have stated is true, but another thing to keep in mind is compatibility.
It can be rather important to create BPs as children if you are ever going to be remapping the assets. (Like swapping out the vanilla dinos for your own versions in the PrimalGameData BP). The reason is this, if you want it to be stackable in any regard with any mods that depend on the vanilla assets then those mods need a way to recognize your new remapped versions. If your new versions are children of the originals then they will match on “Child is class of” and the other mod can cast it to the parent type to do what they need to with it. But if it is a copy then other mods can’t operate with it making your version non-stacking.