Nice looking bike. I was a little surprised at a Tubus rack instead of a Thorn rack in the photo.
The more that I think about it, the more that I probably am happier with my Mk II because I can fit a suspension fork which I have done a couple of times. And if the S&S option is no longer available on the Mk III, then for sure I like the Mk II better as I use the S&S couplers. But the canti brake mounts on the wrong side of the Mk II fork has really frustrated me at times, that was my biggest gripe about the Mk II.
Since I am comparing the Mk II and Mk III, I see a lot of good points on the Mk III. I prefer drop bars, fortunately I could get a M size Mk II frame to fit me well with drop bars, I say fortunately because the bike was designed for use with flat bars. Mk III is available in S frames for drop bars. I like the Mk III paint and graphics better. I would have used 26 in wheels with rim brakes if I bought a Mk III, but I still like the idea of having 650b option for canti brake posts for future changes. And I like the idea of a bottom bracket eccentric that (1) is infinitely adjustable and (2) could be could be set with the crank in either an upper or lower position for minor changes in crank height above ground.
I built up my Nomad with 36 spoke wheels, I am a little curious why SJS is sticking with 32 for a heavy duty expedition bike.