I'm on my second set of KM2's. I have no reason to consider anything else. They work great for me on rocks as well as mud, and my last set provided me with around 40k miles of service and still had enough tread left that I was able to sell them for $75 each. In fact, if it weren't for the sipes getting worn off the two front tires, which made it hard to grip on slippery rocks, I'd still be running them. The sidewalls are very tough, I've dinged and cut through the outer jacket a few time, bad enough to rip off valve stems, crush center caps and bend steel rims, but never punctured a tire.
I've never run the MTR's, nor has anyone in our club. We did have an opportunity to see several well-built rigs at a Goodyear-sponsored event here on the East Coast, all were running MTR's. The tires did not do as well as the non-sponsored rigs wearing KM2's on the often muddy obstacles and hill climbs. The MTR tread did not clear nearly as well as the KM2's.
If you are wheeling mixed terrain, particularly East Coast locations, I feel the KM2's are the best tire you can buy. It is somewhat upsetting that you pay the same price for 35" KM2's as you do MTR's but wind up with less diameter, but if that's a big concern you could go up to 37" for a few dollars more per tire.
I'm a JKO Reject