I'm going to go out on a limb and say neither. For gravel roads and non-technical singletrack, these bikes will be overkill. You could spend the same amount of money and get a real nice hardtail, which will be more efficient, lighter weight, and easier to maintain. I just think at this level of riding, and even on more technical stuff, you don't need 5" travel (on the Mk III at least).
In all, the Meta seems better suited for the kind of riding you do. The extra $200 for the Mk III gets you the nicer fork and suspension design. The extra $200 gets you a lot more but it might be "too much bike" for what you want to ride.