Most people would rather cheat then go through a messy breakup or divorce in order to fulfill their need. It takes more courage to leave than cheat. In my opinion there are 3 basic types of cheaters.
The Incessant Cheater
(Variety is the spice of life. He/she is always looking for something new)
The Unbelievable Opportunity Cheater
(Someone out of their league, an old flame from the past, or a celebrity hits on them) They weren't looking they got "lucky", it fell in their lap...etc
The Discontented Cheater
(Feels neglected/depressed or unhappy in relationship. They feel justified) Someone came along and paid attention to them and filled in a gap or need of some kind.
Monogamy requires maturity, self-discipline, along with the desire to place honesty as the top priority in a relationship.
Cheating is a selfish immature cowardly act of betrayal committed by those who are too insecure to let go of a "known" situation before pursuing a new relationship. The problem with trying to access which sex is likely to cheat is most of the research is based upon surveys and it would be foolish to believe they contain 100% honest replies. Most women and men I know have been cheated on.
(I'm certain women in lesbian relationships would tell you women cheat as much as men.)