Bounties are not just up to the formalities, it really requires you to do a job which will be rewarded after the campaign. Bounties gives decent amount of token/money than airdrops. Most bounties are legit than how most airdrops are just a scam or a trash (no tokens sent). Bounties are definitely effective, the very reason why almost all members here at Bitcointalk.org Jr. member above, join signature campaigns and other campaigns as well. Translation in bounty campaigns pays a lot from the hardwork and effort you've exerted. If I were you, try both or better yet.... do both.