Efficiency of calorie acquisition is not the same as sustainability though. Culling an overpopulation of deer that keeps a forest from developing or an invasive species that is wreaking havoc on an ecosystem can both be a net positive on the ecosystem and in terms of sequestering carbon. Meanwhile growing crops on former rainforest land is a clear net negative.
Those are edge cases though of course and with your average store selection, going with plant-based will just about always be more sustainable.