Cities:
• There are way more people who can replace you, but you may work for a larger company that doesn't even know you exist.
• If you are fired then there are more opportunities for work and you won't be as screwed.
Rural:
• There are less people living there and outsiders would have less incentive to move there for work. People who move to rural areas for work often move out shortly thereafter (Happened at a job I worked at in a rural area), leaving a smaller pool of talent.
• If you are fired, though, you'll have a hell of a time getting another job since chances are you may be working at the only company in your field in that area.