Well the only ones that were "nicer" then the other ones were that which held the Japaneese Americans (Congress ordered because so much paranoia was going on that there could be spies among these people, even though 1/3rd were born in the United States). There was no labor that basically was wearing you down until you died; moreorless there weren't gassings, mass murders, and severe beatings. All of these factors, however, you could've found in German concentration camps.
