Consider the general differences between public and private schools. Public and private services for children on the Spectrum exhibit similar differences. Private services provide more individualized one-on-one attention and address the unique needs/goals of each child. Public service providers are often overworked and under-paid. While some of them have the best intentions at heart, they are often simply incapable of providing the services necessary to help their client reach his utmost potential. -And others are just doing a job rather than pursuing their passion of helping families.
Also, there are political entanglements within the public system that often interfere with the services provided to families (within schools districts as well as public agencies). We all want *the best* for our children. If you have the resources, get your little one the quality services he deserves as early as possible.