IMO - Men cheat more than women. Men can get turned on simply by looking at a two-dimensional image on a glossy page of a skin magazine. Women, on the other hand... well, I dunno. Women like sex too.
I remember having a young couple working for me years ago. They went on a vacation to visit her family and he ended up having sex with his SIL. It didn't end well - she became promiscous, he got some other girl pregnant (they had a baby between them already), she took him to the cleaners in the divorce, she got pregnant by a married man, he divorced his wife and moved in with her, he got another girl pregnant, she got pregnant by another guy and they all moved to Oregan.
I was propositioned once in my life. I was single (she was married) and, unfortunately, I had to decline because she was totally intoxicated and I had this visual of her barfing all over me at the peak of orgasm.