Hi
@stevenA and welcome to the forum.
I think this depends upon the person. For somebody who tends towards constipation, magnesium Citrate would be good.
I tend the other way so I used Magnesium Glycinate (which supposedly also helps with sleep).
From Twitter I know of 2 low carb doctors who also use/used that one, but it is expensive.
I only used it as a part of supplements for electrolytes (Sodium, potassium, magnesium) during the transition to fat adaptation.
Now I get all the magnesium I need from my diet, though I still supplement Potassium via 'lo Salt' which is half Sodium Chloride and half Potassium Chloride - it tastes the same as ordinary salt and is also able as a supermarket 'own brand' under various names.