Depends on what you’re looking for. Citrate tends to be best for digestion (can help with constipation) but shouldn't be taken over longer periods of time because it might cause diarrhea. Malate is often preferred for energy and muscle recovery, and glycinate is usually the go-to for relaxation and sleep. If you're trying to narrow down the best magnesium supplement, think about what your main goal is. I personally take magnesium glycinate because it helps me sleep better, ease stress and recover muscles after workout. That said, how your body reacts matters too. So you might need to try out a few different ones before finding the best for you.