Another factor is the amount of protein that each contains: Google says soy beans are 36g per 100g, whereas it's 24g for mung beans, so you'd need less quantity

Another factor is the amount of protein that each contains: Google says soy beans are 36g per 100g, whereas it's 24g for mung beans, so you'd need less quantity of soy to yield a given amount of protein. As a separate comment: wow, I had no idea mung beans contained that much protein!