John:
I think a lot depends on the tees you are playing from. Dismal River is much longer from the back tees, so it's harder from all the way back. Sand Hills might be harder if you are playing from the same yardage, but not if you are playing from the "same" tees [first set, second set] as I suspect Dismal is longer from each set-up. [We've had the same comparison problem for years between Pacific Dunes and Bandon Dunes ... some people insist one is harder, some argue passionately that it's the other.]
It also depends on which course you play more [sample bias]. In the case that started this discussion, Boehner played more than one round at Dismal but only one at Sand Hills, and we're comparing his best-of-2 or 3 at Dismal to one [with more performance pressure, the day after a career round] at Sand Hills. I would bet anything that most Sand Hills members would find Dismal harder, and most Dismal members would find Sand Hills harder, because of the same selection bias. The course where you're more comfortable is the one that's easier, which sometimes says little about the courses themselves OR about the strengths and weaknesses of your particular golf game.