Preferably Bounty is the best as it offers you many Campaigns to earn from and the rewards are also much higher than Airdrop, infact you can't compare the two. Can't remember last I did Airdrop since I started Bounty
I would stick to the bounty. Airdrop is just a 1minute work, which doubtfully be rewarded. Bounty is something different. Even if you dont earn anything (tokens), you will still know at least something about technology or blockchain. Meaning you will still earn through learning something.
The gained knowledge might someday help you. For example when you are wearing others projects signature, you can show your gained knowledge in the post
