Vitali would knock Cooney out, probably in the early rounds. In order to win, Cooney needed a stationary target that enabled him to unload his devastating offensive. Vitali would not be a stationary target; he would show excellent defense and keep away from Cooney's powerful left hook. Vitali would also counter well with rights, and he'd keep his jab in Cooney's face. Cooney didn't take a heavy punch well, and Vitali's power is well above average. I believe Vitali would catch Cooney with a strong right hand eventually, and Cooney wouldn't be able to recover. Nothing against Cooney, whom I like and who I think should have accomplished much more in his career: he could have been a beltholder if not for his out-of-the-ring problems. But I can't see Gerry hanging in there with Vitali.
A better fight would be Cooney against Valuev. I believe that Cooney would knock Valuev out, in devastating fashion.
Cooney may be the first to drop Vitali here early, but Vitalis superior jab, chin, and defense would be the difference and he stops Cooney in about 10.
Probably a good fight for 5-7 rounds, but I don't think Gerry had the staying power to compete with a man like Klitschko who's size and strength surpassed his own, and was far more durable...
Vitali would have weathered a few good Cooney lefts in the first 2 rounds and then would have taken over and dispatched him in the 4th with 2 knockdowns leading to the ref stopping it.