If it was a few years ago, I would definitely choose bounties over airdops without a doubt. But nowadays, I doubt that choice. I've just joined the IQ Cash bounty last month and got only a few bucks in reward for the work of weeks. If I was lucky enough, I could earn the same money after a few clicks with an airdrop. The point here is you can do either bounties or airdrops, as long as it doesn't affect your daily routine. But generally, bounties take more work than airdrops, so be careful to choose good projects.