In Oz, many prisoners have to change their location from the experimental unit Emerald City and some normal units, and vice versa.
Emerald City is extremely controlled with much more prison officers, and it seems that the living environment is worse than in normal units (There are harly any private things; plus when he was in a normal unit, Schillinger was seen with a personal radio device, playing at a pool table, etc.). Also, there seems to be much more violence within Emerald City than in the rest of the prison.
If I were a prisoner, I would definitly not want to live in Emerald City.
However, a lot of prisoners are even begging for being there, or complaining if they have to leave (e.g., when Martin Querns, the replacement of McManus, began to reorganize Emerald City and exchanged a lot of prisoners. But also during the whole series). Why? What is so attractive for prisoners that they want to live in Emerald City rather than in any other prison unit?