It depends on the airdrop. The best airdrops that I know have been Ontology, Polymath and PiedPiperCoin. But you had to be lucky to get one of those.
The most airdrops are giving out only a very small amount of tokens that usually have at most a value of 5 dollars. That is not profitable at all.
Bounty is way more profitable. One great bounty campaign was that of #Blocnation. Fixed payment for activity. The project itself is great so was a pleasure supporting it. Check out more here: https://blocnation.io/