Magnesium is best bound with a natural chelate (amino acid) as in mag citrate! It would be my first choice if it wasnt for the very inexpensive magnesium sulphate which adds the sulphate and does all the great things MSM claims it does, added to a little fresh lemon, a chelate and distilled water and you have a first rate mag citrate drink with the added benefit of the sulphate!
Most people are already to high in chlorides so magnesium chloride is one of the least favorable mag compounds out there!