The Sierra 140 grain GameChangers are a very good balance of expansion and durability in my opinion. They are a bit tougher than a Scenar or Berger, but not as tough as a bonded or A-Frame type bullet. So, if you are having a hard time deciding, that might fit the bill. Plus, they fly good (at least in my .260 and 6.5C) and are relatively inexpensive, comparatively.
That being said, I completely agree with Feenix when it comes to Black Bear, or Whitetail bullets. There is no "magic". Just put the bullet in the vitals and the animal will die.