hardwood floor: Kahrs vs. Junckers

My wife and I are deciding on whether we should install Kahrs engineered or Junckers solid (clip)on our concrete floor. We don't know much about the clip system and would like your knowledge/experience in this area. Also, we heard that going with the traditional nail down solid hardwood floor is best way to go in terms of long term. Is this true? Please help. Thanks!