Given equal numbers and technological prerequisites I would believe that old Nazis were more dangerous. Neo Nazis are just brutal lowlifes who usually turn to a hateful ideology in order to create the illusion of being basically valuable and good but held back or even oppressed by [INSERT MINORTITY]. Old Nazis were so invested in their collective psychopathic worldview that they could regard the extermination of others as something that may be pleasant or very hard or even sad but in any way just neccessary, so it had to be done.