It’s subjective, of course, and every child is different. Some will thrive in a Montessori environment, and some will do better with a traditional format.
In general, children who are self-directed do exceedingly well with the Montessori method, but those who need a lot of structure don’t do quite as well.
Personally, I love the child-centered/directed philosophy found in most Montessori schools, but like Paramount said, some schools are only posing as Montessori, so do your homework on the individual schools. (Full disclosure: we’re homeschoolers, and I’m a former public school teacher.)