According to SynergySports stats, Hill's a better offensive player than Gortat. There is not much difference defensively between the two and they're both below average. I've heard Gortat described as a rim protector more than once by Celticbloggers and it's not true. He's a big who can score down low, but provides Euro-defense.
Not overwhelmed by either, but there's not much out there and surprisingly, by points per possession stats, they're both better offensively than Monroe and all three are on a par defensively and all not very good.