Bennett is a tough comparison in the NHL these days, because the guys who play on the edge (I'm not sure he'll bring that to the pros) tend to be lower tier guys who are more or less just energy plugs for their respective teams. You don't find it in your top 6 too often, but when you do, it makes for some fun hockey (Perry & Ovi).
I've heard him be compared to Toews, Pavelski, Kesler, Duchene and Killer. I think it'll depend on what he brings to the NHL. If he doesn't fight and rough people up; I think it's safe to say he'll move more into a skill role.
I for one, would be beyond happy if Calgary got an in his prime type Ryan Kesler out of Bennett; pest, fights, hits, plays an incredible two way game, scores 75 points... That'd be crazy. You toss that in with Monahan... you have yourself a Stanley or Two when things are said and done.