I think we should be involved with both.
+ Airdrop: join 1 time/project, easily, get many tokens if you have many ref or many accounts. I know there are people with hundreds of email & Telegram accounts to participate in airdrops;
+ Bounty: participate for a long time, put in more effort => the value of the reward is also greater.
Sometime, airdrop is also a part of bounty campaign.
I rarely participate in the airdrop of a new project, I often participate in the bounty of a potential project or be organized by a reputable bounty management team.