Better at what? At chess cooking, creating videos, as a person? I suppose you mean at what they do on youtube. My answer is - depends on what you are looking for. If you want to see recent or famous game from your favorite player then agadmator should be your go to person. If you want short video covering certain opening then Gothamchess will probably be a better choice. Agadmator also has few videos where he shows how to play some openings and Gothamchess has covered few of historic/interesting games on his channel too, but neither of that is main focus for them. I like both, but if I had to pick I would say Levy, he is more diverse.
Who is better?