Testnet is an essential part of Blockchain ecosystem specifically created for testing and developing new Blockchain application and smart contracts.
Testnet Airdrops can be obtain free of charge without effects on your financial position, no fees are required, one good thing about Airdrops on testnet is that that they pay massively better than Telegram Airdrops.

On the other hand Telegram Airdrops are Airdrop farm on telegram bot.
the explosion of Notcoin got lot of people attracted to start mining Airdrops on telegram at the end of the Airdrop participants will be required to pay certain amount of Ton as gas fee in most of the Airdrops and most persons will give in to the payment of the fee, only to discover that the Airdrop is not worth the stress and time consumed .
It's more preferred to mine testnet Airdrops than telegram for now.