If that Coinbase wallet asks for no fees at certain transfers then those are off-chain, meaning that your friends don't actually own those coins (not your keys, not your coins), instead they have an account at a custodian wallet that holds the money for them, ask for KYC, record all they do and if Coinbase will get bankrupt or hacked your friends may lose their coins.

Instead with Mycelium you have your own keys. Even better, Mycelium can work with Hardware Wallets, in case you'll have more coins there and you'll want to protect them better. Of course, you have to make sure you have a proper backup for your wallet/seed, since with your coins you have to be more responsible (no customer support will be able to recover them if you make mistakes).

I recommend Mycelium. But I reckon that there are many kinds of people in this world and both types of wallets have pluses and minuses, so please make your own choice.