If you would not be using the S&S couplers, then just make sure they are tight and stay that way. It would be best to check to make sure there is no dirt in the threads first, and greased. If you are not using them, maybe the special grease is not needed because you would not be disassembling the couplers.
Often people do not get their money back on the couplers if they sell a bike that has them because most people would never use them, thus would not perceive any value from them.
There is one thing I would prefer on the Mk III, the fact that I could have a derailleur hanger, even if I built it up with a Roholff. Oops, one more thing, the canti posts on the fork are up front instead of behind the fork, I would prefer that.
But the Mk II had the couplers as an option and that was a high priority for me. And after I bought the Mk II, that is when I realized it can be nice to fit a 100mm suspension fork to that frame.
For me, the Mk II is preferred. But everyone has different priorities, you need to assess your priorities. And the Mk II is likely cheaper being used. And the Mk III would be under factory warranty.
