Note
Ask why you should live vegan (step 5)
Alternative to 'biggest advantage': do you know why you should be living vegan? Same answer, animals gain another voice for justice, and you stop being a hypocrite. You don't have to talk about animals separately; it's one question with two benefits.
Gives ammo
What's the biggest advantage of veganism for the planet and your health?
Gives nothing
Do you know why you should be living vegan?