I've read that Grizzlies are more likely to attack, but that Black bears are more likely to continue the attack until death (yours).
Black Bears are alot more common in most states so our contacts are much more frequent. Their population numbers are growing rapidly, so the home invasion rates will increase.
Younger male black bears have generally not learned to fear humans. Rather, these teenagers see us a source of food...both directly and indirectly.
This is just one, of many, reasons to have a spring and a fall hunting season...to try to train the bears.
Black bears invade people's homes and cars for food. They seem to be ok with eating human flesh.
Grizzly bears seem to not like the taste of human fresh as much, so far. Thus they are somewhat less likely to hunt us for food. But they can kill us with one good swing...even if they are not hungry.