Over the years I suppose I've been influenced by information that I didn't know before - which I've read on MN and in other parenting discussion places - more so than by opinions unsupported by anything else. That has influenced my choices.
But I don't beat myself up over decisions that I made earlier just because I might make different ones today - that way lies madness. Either you end up beating yourself up unfairly when you didn't know any different at the time, or you end up painting yourself into a corner defending a decision that you might not even make again if you had the choice, just to avoid looking like you're saying you were wrong.
Really as others have said every decision is less than ideal in one way or another and it's best just to own your own decision - provided that doesn't mean you feel you have to take up a lifelong stance where you label that decision as eternally right for everyone, rather than just a good decision for you at that particular time based on what you knew then.
E.g. with the SAHM/WOHM thing, I think there are downsides to both. I'm not convinced nursery is generally a good thing for small babies but I would still use it again if I had to - but it would now be a good bit further down my list of choices than it was for my older children who were in nurseries as very young babies, now that I know some things I didn't know years ago. But equally I'd be concerned about financial vulnerability if I had to be a complete SAHM (I work part-time at the moment). That wouldn't necessarily stop me doing it but I would work very hard to put things in place that made me less vulnerable - I would consciously adopt quite a hard-nosed business-like approach to planning my own financial future in case of change.
Nothing I've read has ever convinced me that it's best for everyone to be either a WOHM or a SAHM, nor has anything ever convinced me that either all WOHMs or all SAHMs are evil and need to be taken down a peg or two. I'm quite convinced the decisions most people make are best for them at that time given the information they've got, even if my own might be different because of all the things in my life that are not identical to theirs, and even if I'd take a different side from them in any kind of theoretical debate about an issue like childcare.