Honestly it depends on your content. As a gaming channel I don't script because I want to have genuine reactions to gameplay - however - planning the video is very important. I partially script - I get a general idea of what I want to say to intro and end the video, and if there are any updates I want to announce, I do the same thing. I never go word for word script because then it doesn't sound genuine, but planning things out does have benefits, including less ums, more confidence, and a clearer message! If you do decide to make a word for word script, make sure its natural and comfortable to say!