Do you mean the cornish cross that people
usually raise for meat? Because most people say they don't forage, they lay by the food dishes and eat more whenever there's a little more space in them. If you try to put them outside they die in droves.
Some of the other dual-purpose birds will eventually get big, but it takes a lot longer than the 8-12 weeks the cornish crosses or Freedom
Rangers take. With the prices of store chicken being pushed down so much in the US, if you can't finish them in under 3 months you start to lose money on feed
If your pens can support most of their food needs then it's different. My chickens run loose (we have a dog that protects them) and when there was snow on the ground they ate 12 cups a day of food. When the snow melted, they lost interest and went down to just about 4 cups a day, and some of that was eaten by wild birds. I think my flock is around 50. Most sources say on range chickens find 30% of their own food. I think it depends on the breed, but the bigger breeds are more dependent on being fed, IMHO, because they're far larger than the natural state they evolved to sustain themselves in, so they have higher food needs. Something like a game fowl could possibly live on free range after a couple generations but I'm not sure people would be happy with that if they expect one that looks like a store chicken.
Our second generation, what we're eating, are from "Easter Eggers" that were bred by a game cock. I got them from someone whose hen hatched a clutch in their garage, and they've turned out to have excellent brooding and parenting instincts. One even hatched 19 eggs just before the cold weather came in. We took some to raise indoors until they feathered out because with so many she would have lost some. Those are the ones we've been butchering lately. The offspring didn't look like much but when we butchered them they were surprisingly meaty, the bones are tiny so the looks are deceptive.
But free range chickens have a difference in flavor and texture that most people would notice. They're easier to make tough and the flavor is strong, and occasionally gamey (but I don't think unpleasant). People from foreign countries that are used to "real" chicken would probably buy them up, but Americans used to that pasty mush we call chicken breast might not know how to cook with it. I'd say they have twice the flavor of a similar amount of store chicken.
I'd say try a few of the breeds you're looking at from chick to dinner-plate and see what you think. Have friends over to eat them with you and see what they think.