I think you two are locked in a debate that is (no offense) pointless. We all have options and choices in our lives based on our personal resources and circumstances. We choose what we think suits us and our families best. Two of the many many things people consider when deciding how to use our time and skills are to ensure our children spend lots of time with both parents and to ensure that we are as prepared for unhappy eventualities as possible. Neither consideration will rule the decision because there are a million other things to think about. 
 
When I decided to have children, I already had an established reputation that I worked hard to obtain. I had a building that I (and the bank) owned. I had employees who relied on me to be able to earn their family's income (they actually do most of the work but ther has to be a member of the law society to supervise a firm or they can't operate). I have a responsibility to my clients who have relied upon me for years. I also thought about my health because I have a chronic disease and I had to consider my bouts of poor health as an issue. I looked at my husband's career, too and we talked about what he could bring to the table to protect my children in the event of my illness or death. I had other issues relating to my family and my friends.  
 
Being afraid that my child would be injured because they were being cared for by a non-parent or being prepared for the possibility that I might be left as the sole support of my family weren't the biggest issues for me. But I find it easy to acknowlege that they are things that should be considered by women when making decisions. I think you can both acknowlege that they are important considerations, but neither of you can tell anyone else what should be most important to them. 
 
Just as an examply, Sally, you have to acknowlege that someone from a wealthy family with a large, cushy safety net might not worry too much about keeping her skills current? And Diana, you would have to acknowlege that someone living in a more traditional, multigenerational extended family situation might not find their burning issue is being home fulltime. 
 
Can't you both simply agree that those are both important issues to consider?