Their differences are far less significant then their similarities. They both love to kill the innocent, those they consider "inferior" - who can be just about anybody and whose inferiority exists only in the fascist/nazi's imagination. They also love to lie, they lack conscience and are generally sociopathic. When not killing and destroying they both love to march around in silly looking uniforms, oftentimes carrying torches. They also both need to have a strong male authority figure that they can worship and who shares their pathologies and who generally meets an unhappy end.