My two sons went to one of the most highly rated Montessori schools in Santo Domingo -- Primaria Montessori. Would I do it all over again? Not sure. I don't feel the Montessori system, at least in its pure version, encourages reading enough. I feel it is too methodical, and while there are good things to be gained from that, I wonder it if is adapted enough for today's world. I do know other parents, who were very happy about the education.
But what I most treasure from that school experience, was the fun had with the other parents and the good times the boys had with their classmates. The parents (mothers and fathers) always looked forward to the children's parties! I raise the point, because normally one will be with a group for at least six years, the children and parents will teach one another.
My opinion at this point is that there is no sure bet. I would prefer a mix of systems, taking from one and another.
Another point to consider is if the school continues through high school. My boys had to switch when they got to 7th grade. That has its advantages in making new friends, but it is also sad to separate the children, and means that for a second time you will have to go school shopping.
It's no easy chore to find a school. Bottom line, I think you want a school that will open their minds, encourage them to read and write, and be good public speakers. With so much negative in the world out there, you want a school that will help them work on values and strengthen their abilities to recognize what is good and bad for them.
As parents, the reality is that you have to be ready to fill in the voids, but then brave enough to let go so they can work their own way through.