Dota is a good moba, and definitely much harder of a game than league, since there are many more things to pay attention to, which adds an extra layer of depth. But league of legends has a more intriguing art style in my opinion. I'm also not a huge fan of "if everything is op, nothing is op" approach to games. So i prefer league.
League is literally the most popular game out and has been for the better part of a decade. Dota 2 is trash comparatively. That's why the majority of dota players moved over to league years ago. Also because league has a way better competitive scene.