The downside to keeping them contained is you can only keep so many before they become stressed and fight. I built a 8 x 16 run last year and I'm already adding another run so I can add more chickens. Free ranging is a whole different ball game. Unlimited space no fighting.
My neighbor doesn't have a secure run for his chickens but he does set traps. The only way he manages to keep a flock is by incubating his own eggs and hatching chicks.Good luck!