I'm deaf and can only watch TV/video/YouTube if it's captioned. Some closed captioning is better than others, all of it is static-meaning it's primarily presented at the bottom of the screen. It can get very tiring reading captions and following the action, especially if people talk fast or if it's a dialoge-intense movie or if the action is fast. Takes a lot of concentration.
I'm not sure the dynamic captioning will be an improvement. I anticipate issues with the eyes having to locate the text. Now, I can focus on the bottom where I can anticipate the text, read it (fast!), then look at the scene before it changes. If I have to hunt for the text position, then read it and look at the scene I may miss one or the other.
Also not sure whether the different coloured text is an enhancement. I really don't need emphasis in the captioning. The action itself gives that to me. In that way, it's kind of like reading a book where our brains add emphasis to the characters' voices.
I would dearly love to see a sample.