You’re a developer building a new token-based product.

Your goal is to acquire users for your product. You’re considering an airdrop as a tactic to do this.

User A 
History of not selling airdrops immediately.

User B
Sells most airdrops immediately.

You can only airdrop to one. Which one do you choose?

The product uses the token?

Then I'd think user B .. if you want new users you want the token to be liquid and circulate to as many potential users as possible.

Hoarding decreases liquidity.

Dad. Renegade NPC. Seeking balance between level best and happy medium https://nf.td/semui

Developers gives you the token.

You sell it. You don’t use their app. 

How did this benefit the developer?

Ahh you didn’t say you don’t use their app. You just said user an and user b. I would assume both users used the app, if they are receiving an airdrop in the first place.