You'd have to do something really stupid to get nailed by a black bear (don't smear yourself in honey and then line yourself in poptart's - it's all they want anyway). I'm not telling you to leave the gun at home (because you're more likely to run into some bad people than aggressive bears), but don't count on needing it for that specific purpose.
Of the two I would probably go with the .357, but what size is it and which one do you shoot better? A head shot with a with a full size .357 will kill a black bear no question.
Where on the East Coast will you be camping? Car camping? Remember, never cook next to your tent, or dispose of food near it. Don't even leave a snickers wrapper in your pocket. Bear bag properly, or safely store the food in your vehicle.