We looked (and spent 'guest days') at several Montessori pre schools, as well as some local preschools and several of the KinderCare schools. The Montesorri schools seemed a nice package, but very heavy into an academic push - gave us the impression they were saying "if you want him to go to Harvard law, you need to start now and here". They didn't have as extensive a physical facility for indoor or outdoor play activities as Kindercare or the other pre-schools.
The KinderCare preschools also had plenty of planned academic structure such as reading time, music, letters/shapes/numbers, pre-reading, phonics, natural science, different cultures and languages, etc. But they mostly conduct these interspersed with frequent play activities which focus on social interactions development. Lots of emphasis on sharing, helping, taking responsibility, taking turns, leading activities, etc. They also had weekly lesson plan sheets with parent/student 'homework' to bring in some continuity with the home activities, and sent home a daily sheet with comments on physical/social/academic/emotional observations for that day. Also, for toddler to 2 year olds, parents would fill in a daily drop off sheet noting how the child had slept, what type of breakfast was had, and listing any concerns for the day. Kindercare also had the edge over the others with meal service - breakfast, mid-morning snack, hot lunch, after-nap snack.
Ultimately we liked the teacher-student ratio and social skills emphasis approach better, reasoning that self confidence and social development are at least as important as being able to read before you turn 5. So we used KinderCare for the last 3 years, toddler to age 4 class rooms. We have enjoyed the very caring and committed teachers, and have watched our grandson develop into a confident, fun loving, and extroverted 4 year old with an extensive vocabulary and K+ level numbers, letters, etc. skills. Nothing 'wrong' with the Montessori approach, it just seemed learning was more fun at the Kindercare, and learning to interact with people seemed to be a desirable core for the experience. The Montessori program was a little less expensive than kindercare, but the kids didn't look as happy to be there as the ones at the Kindercares we visited.
These comments might not apply to M or KC schools in your area, so it will be worth while to do some extensive checking yourself, and spend a half day or day at the ones you are considering. There are quite a few links on selecting a day care or preschool, including
http://worknwoman.com/worknmom/daycare/what2look4.html. Good luck on your selection!