NWoods,
I'm in Grand Junction, CO so Moab is 96 miles from the house. Those of us who play in the Western Slope of Colorado or in Utah spend a lot of time in the rocks. Before I upgraded to 37's I ran my siped 35's for about 8000 miles (and about 3000 unsiped beforehand) and had no chuncking out on any of the lugs. My Jeep is not a DD and 75-80% of it's miles are offroad. The sipes do great things for performance in rain, ice and snow but they also improve performance on rock too. I wasn't expecting that but have found it to be true. A soft siped BFG Krawler might to better than the siped KM2 but in my observation a siped KM2 is the best offroad tire available today. I pay attention to what the tires on other rigs are doing and based on what I have seen stayed with the siped KM2 when I went with 37's.
I am a fan of siping to the extent that I bought a 200.00 siping iron that can cut four sipes at once with quarter inch spacing. It will pay for itself in in three sets of tires relative to what Discount Tire charges to sipe 5 tires at 15.00 each. You can do a much superior job by hand than the Siping machine tire shops use an would encourage you to go that way. You can get a single cut Ideal iron for about 70-80. If I can figure out how to post a picture I post a pic of one of my tires that has seen use.