Being adequate is enough. Chose something that doesn't seem clearly harmful, pay attention for signs of harm, pay attention for signs that it's a bad fit and make a change if it is. Really all you need from preschool is socialization, and some exposure to germ warfare.
What I hoped for my child to get was familiarity and positive associations with the school concept. In my mind, it's more helpful if young people enjoy school and feel it is a place where they can do things well than if they have a lot more academic skills early and have developed a dislike of school.
Why? Any Prussian model school will inure them to ranking, tedium, busywork, being ranked and doing things that seem pointless because an authority figure said to as well as another, whether they begin education in a child centred school or not. It’s not like most metro areas even have a child centred school, whether Sudbury, Montessori, Waldorf or other. They’ll learn what school is actually like on exposure to it and develop associations with it based on that whether they went to a child centred school for a brief period or not. The long run effects of beginning schooling in a humane system will fade and the only long run effects will be a few better years in childhood.
I suppose that’s enough justification by itself.
I'm beginning to be faced with these kinds of decisions with my oldest.
It's been astounding how well balanced and social all the kids are from that school. I supposed it's anecdata (I only know ~10-15 kids), but there's a lot more awareness and empathy than I've seen from other kids in the 3-5 year old range. Observationally, there is a little less skills development in reading/coloring within the lines.
As a parent, it feels impossible to know the right thing to do for your kids. You have to emphasize something in their education, at the expense of something else. Choosing a school that values the outdoors, empathy, and social development as the basis for teaching seems to complement our tech savvy home life. I hope it works out.