The SDG concentrations in flax seed varies from about 1% to 3%. Since one tablespoon of ground flax seed weighs 7 grams, it contains between 70 mg and 210 mg of SDG. So one tablespoon would have at least as much SDG than the supplements.
Crushing flax seeds is better than consuming whole flax seeds, but ground flax seeds (i.e. flax meal) are superior in terms of lignan absorption.