I'm of the opinion with handguns, even the magnums, for bear defense you don't want to give up any penetration for expansion because they just don't have a surplus of power. I'd be on the fence with the 45-70 but still lean towards the flat point.
Now if you're loading for a true magnum rifle, 338, 375, 416 or 458 then I'd go for an expanding bullet because you have enough power to penetrate from any angle and produce a large wound channel.
