I don't have any first hand experience, but looking for more punch from my AR I looked at alot of ballistics. The 300blk would be the ticket if you wanted a closer range rifle to run suppressed, as alot of the BLK loads will be subsonic and therefore very quiet through a suppressor. Since I live in Iowa, no suppressors for me. I found the ballistics of the 6.8spcII to be far superior for my purposes, but that all depends on how you hunt. I wanted a fairly flat shooting rifle in AR platform for 350yds or less, but also be able to knock down deer/hogs/whatever medium game. 6x45 is lacking in velocity due to limited case capacity, 300blk is too slow as well, 6.5 needs a longer barrel to match the 6.8 velocities to about 300yds... I wanted a 16in hunting rifle, the 6.8 is the ticket IMO if you want a shorter barrel.
Disclaimer - I'm not badmouthing any of the other rounds I mentioned, they are all great rounds for their intended purposes I just found the 68 to be the perfect one for my intended use.