The juice of citrus fruit is a strong cleanser, some stronger than others. Citrus fruit also has more or less sugar (energy). Lemon is probably a stronger cleanser than orange, but lemon does not have as much sugar (energy to run your body) as orange.
So Master Cleanse uses maple syrup (sugar energy) with lemon (cleansing agent). MH advocates orange, which has both sugar and cleansing. Which is best for fasting and health? Big argument.