Whether a cheating spouse is forgiven may depend on the type of affair, with women more upset by emotional affairs, while men care more about physical ones, according to a survey by cheaters' website Victoria Milan.
Men overwhelmingly believe sexual affairs are worse than emotional affairs, while most women consider emotional cheating the "worst-case scenario," at 72 percent and 69 percent respectively, the survey of 5,000 of the website's users showed.
(Read more: More spouses are cheating -- financially, anyway)
That plays into how likely a cheater is to get forgiven: 76 percent of the women would forgive their partner for a sexual affair, while only 35 percent of the men would, the survey found. This contrasts sharply with the mere 30 percent of women and 80 percent of men who would forgive emotional cheating, the survey found.
"What kind of cheating is more painful? It totally depends on the individual and maybe on gender as well," Sigurd Vedal, Victoria Milan's CEO, said in a statement.
(Read more: Why employers should watch unfaithful spouses)
How common are these types of affairs? A 1983 survey of infidelity among U.S. married couples found 31 percent of men and 16 percent of women had a sexual affair with no emotional involvement, while 13 percent of men and 21 percent of women had been romantically but not sexually involved and 20 percent of both sexes had engaged in affairs including both sexual and emotional factors.
To be sure, the Victoria Milan survey only looks at the attitudes of users of the website, which describes itself as an "extramarital dating site," but it does suggest cheaters won't necessarily forgive their spouse for doing unto others.
(Read more: Cheating App: Dangerous Liaisons Get Less Risky)
In addition, divorce statistics suggest the forgiveness theory may not work in practice.
About 23 percent of men and 19 percent of women cheat on their spouses, according to a 2011 online survey of around 900 heterosexuals by Indiana University.
The percentages aren't too far off from the reasons couples give for seeking a divorce: An AARP survey found about 27 percent of divorces around mid-life and beyond were due to cheating; Australian government statistics found around 20 percent of divorces were attributed to infidelity.
But bad as they may be, sexual and emotional cheating don't appear to be the worst type of betrayal when it comes to breaking up relationships. That crown belongs to financial infidelity.
One-third of people who have combined accounts said they have committed financial deception, while 35 percent said they have been a victim of it, according to a study from the National Endowment for Financial Education conducted with Harris Interactive.
(Read more: Adultery website makes aggressive push in Asia)
In an American Express Spending & Saving Tracker survey released this month, 40 percent of women admitted to hiding purchases from their partner.
Three-quarters of consumers experiencing financial deception saw some relationship fallout, with 10 percent getting divorced as a result, according to NEFE. The Australian government statistics found 30 percent cited financial problems as a reason for their divorce.
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter