The reason we watch Reactions is just plain psychology. We wanna experience what we felt the first time watching the scene and we kinda get that by watching others experience it. That said, Hibou is my favourite for the anime. Uzumaki is good too but sometimes he just overdoes it, for me at least. As for manga, I kinda like Rogersbase. An unpopular opinion I know, but its just that I've been watching him for a long time.