Depends from a planet. See, the hive planets are usually overcrowded and violent places and are hard to survive in if you are not one of the nobility. We alco have military planets such as Krieg or Cadia, which are completely dedicated to war, and of course planets that are close to Eye of terror or other alien empires. Other planets might be more peaceful, but since Chaos forces can spawn practically anywhere in the galaxy and Tyranid hive fleets are also hard to stop, there is really no planet where peace can be fully granted. Personaly I believe that most peaceful planets exist generaly in Tau empire. Sorry for my bad English.