My take on free ranging anything is this: it is definitely more enjoyable for the animal and certainly has nutritional benefits to the critter and the person eating its products if applicable. However, it also has a laundry list of inherent dangers, mostly relating to predation and roaming beyond the relative safety of one's property. You need to strike a reasonable balance between the two: keeping your birds safe, and keeping them happy. Supervised free ranging sessions are probably your safest bet. You also need to understand that there is a chance that a predator may eventually kill some of your free ranging birds, and when it happens, it isn't the predator's fault; protecting domesticated animals is the responsibility of the caregiver, and making an active choice to not contain chickens means accepting the risks.
I personally have always been too nervous to allow full on free range. I always simply built large enclosures. I would love it if my birds could safely roam, but after watching my neighbor lose all of her free range chickens, ever year to hawks, dogs, cats, coyotes, etc. I simply wouldn't be able to live with the guilt of it. I see it the same why I see all of my other companion animals: I'm sure the dogs would love running loose in the five acres of woods on our property, but they live in the one fenced acre because it is safer for them. I'm sure my bunnies would love to roam the front yard grazing all day, but they are in enclosures to protect their safety. I KNOW my parrots would love to be out loose in the house all day, but there are too many dangers even indoors for that. Are there other people who do things differently? Absolutely, and that's fine. Just I personally can't deal with the thought of my pets being injured or worse, and am willing to sacrifice some degree of their freedom for that.