I think Lorraine is more reliable and level-headed. Usually people get along best with individuals who are a lot like themselves. In this case, John and Lorraine have very much in common. They both have a wild sense of humor, a dramatic sense of adventure, and similar grievances about life. However, although the two get along and have similar personalities, Lorraine is the more mature of the two. You can argue that it's because girls are said to mature sooner than boys, or because that's just the way her personality is, but one cannot deny that John is more of a cut-up. He's not a liar, nor does he exaggerate, but his flair for being funny and stirring up trouble make him seem far less dependable as a narrator. Lorraine, in my opinion, tends to stick more to the bare facts. You didn't ask for specific quotes or examples, but there are numerous ones throughout the book.