Of course airdrops are worth it, the only thing which you risk is your time. Either by applying to hundreds of different airdrops or by doing a research for a quality ones. Picking only quality airdrops is better strategy, even though it might not always be easy, but it would help to reduce the number of poor quality airdrop projects. In case of ICOs, you have to spend not only time for research, but also your own money so the risk is much higher.