In reference to the statement that AMS "stole" the Montessori name from AMI, that is simply untrue. It's a complicated history - I know because I have visited two AMI training centers, one AMS training center, an AMI school and an AMS school, in hopes of becoming trained as a primary guide.
Because a central feature of Montessori's writings are education and peace, the efforts to work amicably and honorably beside each other are more important than taking shots at each other. The bottom line is the true nature of the child. As I have been told by trainers from both groups, there are good schools and not so good schools, good teachers and not as good teachers. It is true that AMI is the association that follows most closely to Dr. Montessori's writings, but it is also true that there is little room for variation.