Cut on Contact is my preference now, many to choose from like Montec G5, Magnus, Steel Force, Muzzy Phantom..etc. I like COC's for tougher/thicker skinned animals, as they have shown better penetration on such animals with the lighter setups used now(arrows, BH's, etc).That saidI have had excellent results with quality fixed BH's(Muzzy, Thunderheads, etc)as well. I don't like nor suggest mechanicals for larger then deer species.

In terms of black beara larger cutting surfaceBH's isn't a bad consideration, they tend to leavepoor blood trails due to the length of hair/nature of their hides...so any little bit helps.As long as it does itwithout comprimising the relability of the BH.(I say this as I personally would rather have a 1 1/8"fixed/COC cut vs a 2" from a mechanical. Also accuracy is part of the equation, I wouldn't change unless it gave me the same confidence level. Most important thing is putting the arrow where it will get the job done and thus accuracy/confidence/etc are still the keys to selecting the tools)

Good Luck and forget about a whitetail -broadside and behind the shoulder. Bears vitals are tucked up and a large portion of the lungs is obstructed by the larger front shoulder on a pure broadside. If such an angle is presented the best shot will be afforded when the nearest front leg clears forward (stepping motion), leaving the near side lung exposed and assuming you put the arrow in the area a gauranteed double lung and very short track. The 1/4 away is my favorite and has always produced blackie's down with very few yards travelled after the stick.

Use that opposite leg as your aim point and drive the arrow right through to get a double lung and you'll claim your first bear