Compare Jimmy and Bob. How are they different from each other?

In the short story “After Twenty Years,” by O. Henry, we are told that the characters of Jimmy and Bob were, as young men, great friends. They were so close that, as young Bob left New York City to head west and make his fortune, the friends hatched a plan to meet again at the same restaurant in twenty years with the absolute confidence that they both would. And, indeed, they both did.
But, despite this similarity, as middle-aged men they are very different people from one another. Jimmy never left New York City. Nothing, we are told, could have pulled him away. We later learn that Jimmy is a cop, “strong and important,” as O. Henry writes.
We also learn that Bob has been all over the west and that, unlike Jimmy, he’s never made a real home anywhere for long. “I moved around everywhere, and I moved quickly,” he says. Still, Bob’s absolute belief and faith in Jimmy and his goodness never falters, which is a contrast to Jimmy. Although Jimmy has been loyal to Bob in the past, he is now more loyal to the law, and, although he can’t arrest his old friend directly, Jimmy nonetheless finds another cop to arrest Bob, who, we learn at the end of the story, has become a wanted criminal.

Bob is a very well-dressed man with a large jewel in his necktie. As this would suggest, he's also clearly a very wealthy man, an impression confirmed by his fine pocket watch covered with small jewels. Everything about his demeanor suggests great confidence and self-assurance. Unfortunately for Bob, he's a little too confident, divulging to the cop all the details about his life out West and about his planned reunion with his old pal Jimmy Wells. This confirms Bob's identity and allows the cop—who of course is none other than Jimmy Wells himself—to set Bob up to be arrested. Jimmy is able to carry out his duties as a police officer because, unlike his chatty friend, he's much more cautious in revealing personal details. He'll happily engage his old friend in conversation, but he won't forget that he's now a police officer and not the Jimmy Wells of old.