Hi chris.siret,
Both apps work pretty similarly, but have some minor differences. It's not necessary to choose but if you are finding that one isn't working well for you, the other may work better. 😅

I'm afraid this isn't too helpful, but you can definitely use either one to create some basic applets/zaps to connect Google Calendar and Remember The Milk. But please let us know if you'd like any help working with those! 💙