Live and you learn. If its with a neighbor, and you trust your neighbor, best to settle out of pocket. But if its some random person on the street, do not take the chance. One of my friends had this lady hit him, the damage was minimal, and most of it was to her car, and she begged him not to file because if her insurance went up she would go bankrupt, etc. etc. etc. She ended up giving him $200 cash, which was less than his damages, but he accepted out of a favor to her and did not file an accident report.
Two weeks later he got a letter from the DMV that he did a hit and run and that he was automatically at fault for the accident because she filed and he didn't, even though all damage marks on the car show that she hit his car, not vice versa.
Moral of the story is: its a risk either way, you gotta know who you can trust.