Let's start here: One may have ethical objections to "conventional," non-free-range chicken production, and nothing in this data can change or even shape that conviction. In fact, I find myself in this camp.
But I wanted to be intellectually honest with myself, too. Was conventional chicken production, which has been relentlessly optimized by farmers, more or less energy intensive than free-range chicken raising?
Free-range chicken production appears to be environmentally destructive. It uses more land, puts out more carbon dioxide, and uses more energy. That's according to British researchers A.G. Williams, E. Audsley, and D.L. Sandars, which was summarized in a 2010 paper in the journal Livestock Science, "Comparing environmental impacts for livestock products: A review of life cycle assessments."
It should be noted that beef production was far more resource-intensive than chicken. So, one answer to taking less of a toll on the land, while still buying free-range chicken would just be to cut back on beef (or meat, in general).
I see the utility of this data not just in narrowly saying one method of production is better than another, but in helping us see the systems operating in our world. They are so complex and so often hidden from us that we can't make these sorts of determinations from intuition.