NK is just a big nazi concentration camp. They still have that ideology that goes from Mao's cultural revolution in china, but north-koreans had added to it their juche-songun ideas. There was nothing like that in the USSR.
What about russian labor camps, ppl usually prefer to go there then to stay in prison cells. And I don't think the US system of private prisons is ever better then any labor camps.
North europain prison system is good (but the problem is that in europe is amazing level of mass media censorship so i'm afraid we don't know much about it). But the best prisons are in japan and singapore i think.
http://juche-songun.livejournal.com/