Just sparred david more than 8-10 matches, he won once or twice by 0.5-1hp
One of them was early, and the other one was when I dropped to 400ms.
Basically the higher you go, the tougher you are to beat. Even if you only add 70-80ms to what you should be, you have a slightly higher advantage.
By far, david is one of the toughest people to fight against with delay, most of my matches were won by 1hp. Without delay, I have to try and react very fast in order to win. With delay, it's just swing early, and much easier. The only thing I hate about it, is that the matches are boring and long.