This is a really interesting discussion. I've tried raising both Cornish Crosses and Freedom Ranger type birds, and I have to say that I feel the latter is more 'natural' (in my own definition of it anyway).
I personally didn't feel like I was being a good steward of animals by enabling a system that produced an animal unwilling/unable to move from it's own filth other than to engorge on more food. Frankly, it was depressing to even look at them. They did produce meat that was higher quality than what I could get in the stores, but not enough to make it seem worth it.
The freedom rangers were an entirely better experience. They did take longer, but they clearly had the capacity and enjoyed doing normal 'natural' chicken things. They didn't sit in their own filth and just heave themselves up to go eat all day. They ran about, ate bugs, could breed, and did normal chicken activities. And in the end, they yielded sweeter and more delicious meat than the Cornish Xs did. It was very interesting, as I wasn't expecting the difference at all.
When I start a meat flock again, I'll definitely use the Freedom Rangers, and I'll sustain them permenantly. No going back to the big commercial giants, hat in hand, every year for more. That's what feels 'natural' to me.