There is, in some quarters, this idea that the software makes a difference. It's not true. I used to work for a small company in vancouver who edited script for hollywood films. I had ton se Final Draft so I have a copy of FD8. Because I write a lot of actual scripts, I also have a copy of Fade In, which is quickly replacing Final Draft in some areas and was much cheaper than the 8-9 upgrade.
For youtube, however, I just use the notes apps on my iPad. You only need something fancy when you're trying to sell it and the formatting needs to be right.