I'm not sure if it's a case that girls are "better" at cheating or if it's a lot of guys are so self-centered or take girls for granted and ignore "red flags". The number one thing that causes suspicion of cheating is when your mate's known habits or behavior (changes).
Some people just "roll with it" and others (question it) or look for an explanation. In order to catch someone cheating you must suspect they're cheating or at least (feel) that "something" isn't right.
Over 75% of all relationship books, articles, and magazines are read or purchased by women. This would suggest they don't take relationships for granted as much as men do.