I joined several airdrops before, I still don't participate in bounties because it takes too much time to get rewarded. But when I knew that airdrops are useless, i have to switch in bounty and it is better for me than airdrops.
I took part in airdrop and bounty. By the experience I can tell that it is much more effective to participate in bounty. Though you also spend time more, but also can receive payment good if you choose the necessary project.