Having spent a bit of time at Hunters Point Guide Service that past 10 years or so I've seen plenty of bow killed bears. First, only broadside, double lung shots should be attempted. Second, regarding broadheads.....sharp is key...really razor sharp is best. I like multiblade heads like the Woodsman, Razorcap and Muzzy Phantom. The two blade  head that I have seen that has impressed me the most is the STOS...good blood trails and short ones.  This bruiser was taken with a home made bow and arrow tipped with a STOS head. The bear was down in sight.

Shot through my bear last fall with a Woodsman Elite. Shot through the buck I got as well. That head really impressed me. Both animals went less than 50 yds.

I shot my one and only with a magnus 4 and it went dead.....

Agree that a sharp head well placed is key. I've been fortunate to kill half doz. bears and have used both 2 & 3 blade heads. But what happens if I mess up, and say hit the scapula? Settled on Zwickey No Mercy SB heads after testing on green Bear shoulder blades. With 52# LB, shot through the scapula leaned against a stump and then had to hammer & chisel the broadhead out of the stump heartwood. Not the most scientific test, but made a believer out of me and took last 3 bears with that broadhead. Hope this is helpful. Todd

I've only shot a handful, and all with 2 blade heads.  On boiler room shots any decent sharp head will do.  On less than perfect shots, the multiblade has the advantage of a larger hole which helps with how bear fur soaks up blood.  2 blades have the advantage of upping the odds of an exit wound.

I think a wide 2 blade or a skinny 3 blade is a good balance, but whatever I'm shooting at the time is probably what stays in the quiver.