That's 1 good scenario, most are not like that. I don't think it can ever be preferable to have 1 parent over 2. I'm not doubting that 1 parent can do a good job, but 2 can do better (assuming happy marriage and all that jazz).
Sigh, this is what I was trying to avoid. I don't really enjoy debates anymore because they seem to do more harm than good. That's one scenario, yes. However what good would it do to discuss the meta data from thousands of case studies because it won't result in either of us changing our minds. I'm not going to see it differently and neither are you so it's probably best to just avoid it.