Which of these 2 types of people do you think would take a rejection harder?

Person B! From your description, I would think that person B would be the type of person that would have to get up a lot of nerve to even ask someone out. So, because they already think of themselves in such a low manner, they'll be even more devastated than person A. If rejected, Peron B would think to themselves "Oh well, the right person will come along . . . eventually. I knew he/she wouldn't like me." While Person B's response would be "Oh, i'll just try get with Person X, Y, or Z instead. It's the other person's lost." Other scenarios would be the same. And it's not a matter of being attractive, it's more so of an inside thing.