The problem with Malic Acid is that it is too reactive for most people to take daily, also I do not know if Malic Acid chelates Aluminum like Mag Malate does.
Certainly taking Mag Malate daily is a LOT easier on your gut.
I do have pure Malic Acid in my cupboard, it is much more effective during gallstone attacks then using Mag Malate. But I don't want to take it every day which is really what ssems to be required to melt the tiny stones coming out of the liver...from a different angle: http://aor.ca/int/related_research/magnesium_malate_renew.php