Airdrop: The majority of airdrop you just fill in the registration form, higher then ask for like or follow facebook & Twitter. In short, airdrop is a one-time task and you lose 3-4p to register an Airdrop. So airdrop is the one that is registered to do not select anything.
Bounty: Bounty also has to fill in the registration form as Airdrop, but requires higher missions. It's a must to share & share their 3-5 postings per week. Share is much. In addition, each bounty can request and have different rules may be: must join their telegram channel or post the link you share in their topic bounty on bitcointalk.org or share the hashtag ( #ICO #ETH ...), or ask each day to share only one song . Some require you to report ahead of time and if you miss a week do not delete it all.