Airdrops are not worth itat all. For example There is airdrop of 50000 worth of tokens for 2500 first registered members how much you will get after end of ico is 20$ worth of tokens but you will not know whrn it is going to hit exchange and what will be the value of tokens.
I participated in many airdrop and i got few bucks from it. sometimes i got 5$< 7$ that's it.
There are legit project also which can offer larger airdrop for participants but number is very few for these kinds of projects. That's why i prefer bounty over airdrop.