Usually, airdrops are used to increase the number of follovers in project's social networks. I don't think there are any investors amoung airdrop participants. Usually, 90% of them are bots.
I think that airdrop would be good for this project as well. It will help to build numerous community and will help to promote the project while sale is running.
I can see using the Airdrop to get a lot of people to join the ANN or Telebram group because air dropping them SANA tokens is paying them to join but that does not mean they will ever invest just because they got free tokens. I have lowered the minimum so that for only $90 and investor will get 900 SANA tokens plus a free 20% bonus giving 1080 SANA tokens. Basically that means I am airdropping 180 tokens if someone buys 900 for only $90 or 0.007528 In BTC or 0.397915 in ETH. So if someone will not do that, I do not see them buying tokens because I have air dropped them free tokens.
And I have been advised that airdropped just get a lot of BOTS joining.