Personally, I prefer soy milk to cow or oat milk because it has a better nutritional profile. It has less sugar and fat, and more protein, as well as having fiber. (Some oat milk brands do have fiber in them, but most of the ones I’ve found are very high in fat, sugar, and calories.)

Edit: And I like the not-overpowering vanilla flavored ones because I pretty much only use it for cereal or to accompany cookies.