However, if you keep your chickens confined, even if the run area is roomy (defined as 20+ square feet per bird), their lives will absolutely be more... boring. They'll be more likely to peck one another, a headache for you (and worse for them!), and less healthy overall. They'll also require more of the feed you have to buy for them, as opposed to eating the grubs, worms, weeds-- even mice and moles!-- that they find while foraging. Their eggs will be less nutritious if they don't have access to pasture.
We My Pet Chicken "peeps" mostly choose to let our chickens range.
Even if they're not free ranging, they have some confined range or supervised ranging to keep them entertained. (Read our blog about four ways to provide ranging options for your chickens.) Once you've seen how excited your flock becomes when they know they're about to be let out, it's really difficult to deprive them. We feel that the trade-off is worth it: quality of life vs. our own devastation over a loss. We certainly don't judge those of you who just couldn't bear to lose a beloved hen or rooster, though. Just make sure your run is extra-roomy: it'll still be a TREMENDOUS improvement over the lives commercial hens are forced to endure, even in so-called "free range" conditions.
Finally, don't stress too much about these decisions before you get your flock; over time you'll find a balance that works for you AND them. You wouldn't be here, reading this, unless you were a caring and wonderful chicken owner to be!