Of course board scores and grades play a role into your future, but so does a lot more.
Some of the larger DO schools with established residency programs tend to take their own or students from local DO schools, as these are the students they are most familiar with.
Allopathic residency programs in major cities are more likely to take DO students from local schools...again, this is who they see on rotations. They also work with graduates from these schools on a regular basis in their hospital.
Older, more established schools have had scores of classes come before you who are already in that hospital as students, residents and attendings...that helps enormously.
Older, more established schools generally have a larger base of hospital affiliations and post graduate affiliations (OPTI). Larger schools also benefit from this as well, as do state schools.
Not all DO schools have their own residency programs...some have only 2-3 programs, often primary care only.
If you dont want to rank DO schools prior to matriculation and you want to argue all over SDN then thats fine. But I guarantee you Program Directors rank schools. Maybe talking with some of the people who are making these decisions about graduates would be a good idea. I have talked to these people and I can tell you that it does matter.