You can ' t really work this out without picking arbitrary numbers or considering a wide range of variables . The actual value for armor , attack damage and attack speed will all affect the result so even if you try to answer the question for a specific scenario , it ' s not particularly helpful . my general advice here would be down to judgement in the moment you need to quickly think which will have the biggest impact and also consider your cast range . Often if you are a support buffing a carry , you can ' t get close into the fight to cast it on an enemy anyway . I would reserve using it on enemies for heroes that your team is focusing , rather than just generally using it because you can . If you aren ' t focusing anyone then I ' d say it ' s generally better to use it on an ally in a teamfight .