Today in the obvious, 2 > 1. "...divorce tends to double a child’s risk of a serious negative outcome."

Single Motherhood: Worse for children.: "It is true, as Roiphe believes, that most children from single-parent homes turn out fine. In her book, For Better or For Worse, psychologist E. Mavis Hetherington estimated that about 75 percent of children of divorce suffered from no major pathologies. In other words, most children of divorce do not end up depressed, drugged out, or delinquent. But Hetherington, who like Roiphe embraces changing family structures, also was honest enough to admit that divorce tends to double a child’s risk of a serious negative outcome. Specifically, she found that “twenty-five percent of youths from divorced families in comparison to 10 percent from non-divorced families did have serious social, emotional, or psychological problems.” Other research suggests that the children of never-married single parents tend to do somewhat worse than children of divorced single parents...

Take two contemporary social problems: teenage pregnancy and the incarceration of young males. Research by Sara McLanahan at Princeton University suggests that boys are significantly more likely to end up in jail or prison by the time they turn 30 if they are raised by a single mother. Specifically, McLanahan and a colleague found that boys raised in a single-parent household were more than twice as likely to be incarcerated, compared with boys raised in an intact, married home, even after controlling for differences in parental income, education, race, and ethnicity. Research on young men suggests they are less likely to engage in delinquent or illegal behavior when they have the affection, attention, and monitoring of their own mother and father. 

But daughters depend on dads as well. One study by Bruce Ellis of the University of Arizona found that about one-third of girls whose fathers left the home before they turned 6 ended up pregnant as teenagers, compared with just 5 percent of girls whose fathers were there throughout their childhood. This dramatic divide was narrowed a bit when Ellis controlled for parents’ socioeconomic background—but only by a few percentage points. 

The research on this topic suggests that girls raised by single mothers are less likely to be supervised, more likely to engage in early sex, and to end up pregnant compared with girls raised by their own married parents. It’s true that poorer families are more likely to be headed by single mothers. But even factoring out class shows a clear difference. Research by the Economic Mobility Project at Pew suggests that children from intact families are also more likely to rise up the income ladder if they were raised in a low-income family, and less likely to fall into poverty if they were raised in a wealthy family. For instance, according to Pew’s analysis, 54 percent of today’s young adults who grew up in an intact two-parent home in the top-third of household income have remained in the top-third as adults, compared with just 37 percent of today’s young adults who grew up in a wealthy (top-third) but divorced family."