what are the main differences between federal and state penitentaries

The main difference is the federal budget is $7 billion/year, the inmates are well fed and well cared for with a lot of programming options. In general, the guards are paid better and trained better. The state system is as different as the 50 states they are in. Some are okay and others are miserable - like no air conditioning in the hot southern summer. We would say with 100% surety that the federal penitentiaries are better for the inmate than in any state.