heres what I thought happened in the fight, first sentry taking hulks punches didn't weaken the sentry at all in fact he wanted it he wanted to fight and to finally unleash and taking hulks punches somehow knocked it out of him, as he said after one of the punches "thats it" or something like that and unleashed his power then they were going equal however I didnt see sentry managing to land a hit on the hulk after he was unleashed as he was in awe of his power and sentry realized if he wasnt stopped he'd kill everyone and he knew that the hulk had to win or every one would die
then it gets fuzzy, they both depowered, it's obvious the hulk didnt run out of energy as he still had the glowing green eyes and I'm pretty sure he's been said to be an infinite power (unleashed a couple of minutes later) hulk won the fight because he was up sentry was down and bcause he had more hits on the sentry as well, in my opinion hulk took it over the sentry because sentry has no control over his power while hulk has more control