I think Bounty is more effective. After entering the 2018, I did not see any valuable airdrop projects. Many projects do not have airdrop to attract people's attention and achieve the purpose of publicity. Now the ETH gas fee is relatively high, many projects may consider that the cost will not give you tokens.
Bounty is safer and saves time than Airdrop. But sometimes Airdrop can surprise us with the coins we get. My advice is that you should try both