I had better luck with my duratracs than my at's. The firestone mt's do pretty well, and so did my procomps -- in mud that is. Though I haven't had km2s, my experiences wheeling (and driving -- and riding-- their trucks on road) with friends who do would lead me to believe there are better tires out there, especially for on road. I'd go duratracs between those two options. If given mt/r vs km2 I'd go mt/r. I'm running 1 mt/r and I like it so far LOL.
Again it's subjective and my opinion but I'd go with another MT over the KM2 or go with the duratracs.