Here I am, Boomer Treadwell taking my pet bear for a walk before lunch.
But all joking aside, all species of bear can exhibit behavior that is dangerous to people. The situation you are in with any particular bear might be dangerous or benign, and it can change from one to the other very quickly. I'm not comfortable with the notion that one species is more dangerous than another, because in my experience it is the circumstances at the time that dictate the outcome. But from what I have read and heard from people who have worked with both polar and grizzly bears, the grizzly is less social and has a larger personal space that could trigger a negative reaction once entered.