The reality is that there is no right choice here. SAHM risk their kids being on the poverty line and their own long-term financial security (because nobody can guarantee a SAHM that her DH won't sod off with someone from work, even without the risk he may lose that work) but provide them with the security and comfort of having a parent there whenever they are. Their school days are restricted to the hours they are there - the day starts and ends with the school gates, and then they can relax. That's not a small thing. But nor is poverty.
A WOTH mother provides her kids with financial security, if she has a partner - there are two jobs to protect them against financial disaster. She also provides them with a better standard of living than they could have without her salary unless their father is a high earner. If she isn't someone who finds small kids interesting, she provides them with potentially a more engaged and stimulated carer, and if she enjoys her job, she's providing them with a more engaged and happy mother when she is home, too. Finally, she's setting them a great example in terms of work ethic, and the notion that women also work and careers aren't a male domain.
There's also the aspect that staying at home chops a career off at the legs, and lots of it is boring drudgery which can really hack away ar your self esteem. While kids need to be a priority, they aren't the only people in a family to matter. A woman doesn't have to sacrifice her life completely to still be a good mother, and nor should she have to. She matters, too.
However, I don't think most of us can argue against the idea that children prefer to be cared for in their own homes, and preferably by their own mothers. School days are a lot shorter than working ones and while a top notch nanny could probably provide excellent at home care, few people can afford one. That's why so many women go part-time... or stay at home.
My mum had to work fulltime. She was a single parent. I used to know what her car engine sounded like when she came to get me from the childminder. I hated school desperately so after-school clubs and summer ones were purgatorial extensions of my school day. I was so, so envious of my peers, whose days ended when Mum collected them at the school gate. I can remember playdates there and the way they just relaxed because their day was done. Mine wasn't done until 6.30. But looking back, we'd have been so poor had she not worked that my childhood would have been abysmal beyond belief. She was pretty bloody poor as it was. Work made the difference - I know that, because she lost her job when I was a teenager and having her around did not compensate by then for the terrible anxiety about money. If only one of a couple works, the children are exposed to that. Which is best? Who can say? They're hard choices, either way.
What would be nice is if we could all respect that other women are doing the best they can with the circumstances they are in. It's not a criticism of our own decisions, if they chose differently. Surely what works for a family is what works for the child? It's not holy dogma. And the venom people on both sides aim at one another says sod all about either choice, and a huge amount about the people speaking.
This reminds me of the whole breastfeeding thing. Breast is not always best. Sometimes, it can be the worst. For all concerned. But that doesn't mean, if all else is in place and it's working beautifully, that that isn't the ideal - it's just that statistically it is blatantly not that simple.
Most women would lie in traffic for their kids, if they needed them to. If a lot are not breastfeeding, and not staying at home, it's not because they are stupid or selfish. It's because other factors have to be considered, and when they are, working outside the home, or using a bottle, is best for that family and that child in that situation when you take all factors into account. And shaming in either direction is pretty shitty.