Well, if your starting a promotion, as the OP says, there are two vastly different ways to think about this.
On the one hand, Matt has been proven to be a fine commodity, is (well...was) the most over mid carder, and depending on the size of the situation, you go with him. He is the safer bet, as he has been relatively injury free, and always dependable.
Jeff, on the other hand, is Jeff. Hugely over, and would probably draw you a lot more money, but for how long??? He has a multitude of nagging injuries, and chronic back, ankle, and neck problems. This is just speaking on the his body, and of course, the unreliability of his mind, and character. While he may have moved past THOSE demons, his mutlitude of physical problems will catch up sooner than later, especially with the kind of style he works. If you were starting a promotion, Matt Hardy would be far better, and safer, to build around.