Magi: The Labyrinth of Magic already has a second season called Magi: The Kingdom of Magic. No Game No Life, on the other hand, doesn’t have a second season.
I’m going to say No Game no Life, the main deciding factor being that Magi’s manga is completed and fully translated, so at least u can finish the story, unlike NGNL.
I will say magi since it is an amazing show (not saying ngnl is better). The manga is also finished so there is a lot of material to adapt. While no game no life is still ongoing