If there's one video that shows off the purposefully confusing Google+ and Youtube integration mess, its this one of a woman literally crying because of it. Warning: Strong language https://www.youtube.com/watch?v=Ccxiwu4MaJs
It seems that a deleted YouTube channel can still be recovered and that the only thing that's lost is the views, private messages, and comments.
The reason this lady deleted her account was that she was tired of receiving notifications, that setting can be changed here: https://plus.google.com/u/0/settings