Right, airdrops require you less tasks and you can join airdrops everyday but the reward is less and considering that now lots of airdrops are not giving their token. Bounty will gives you more rewards if the project is succesful and also some if them are noy giving rewards as well. If you don't have much time doing bounty or you are not use to it then airdrops I think is better for you. The only thing to consider here is you must carefully choose only which you think is legit.