One side claims that it punishes its victims, regardless of the severity of their crimes or lack thereof. The second argument concerns what the Otherworld does to its victims.
Another side claims that the Otherworld temporarily replaces Silent Hill, which leaves forensic evidence after the shift ends and has at least once caused severe damage to the normal town. One side claims that it is a parallel reality which abducts people, while Silent Hill at large remains a pleasant resort town. The first argument concerns what the Otherworld is physically. I have seen two arguments, each with two competing sides, for how works the Otherworld (and fog world, dark world, nowhere, etc) within Silent Hill. It has been years since I heard the debates so correct me if I am wrong.