ok so i've driven both on the same spec rims only 2 weeks apart on the same tracks with no weather variations (ie: it still hasnt rained).
BFG KM2:
On-Road - Quiet, corners well, no significant tread wear
Offroad - 10psi, grips rock, shale and gravel very well, a little loose on powdery clay surfaces but gets there in the end.
Mud - haven't had any to try them in.
Kumho KL71:
On-Road - Quiet, corners well, can't comment on tread weat but compound feels similar to KM2.
Offroad - 10psi, grips rock well, although lost traction slightly more than the KM2, shale was fine and gravel i think gripped better than KM2, powdery clay it just owned the KM2. Where i spun all 4 wheels on KM2 the KL71 just bit in and chugged up the hill.
Mud - haven't had any to try them in.
Thus far though i can honesttly say you'd be splitting hairs between the two, and given the KL71 is near enough to $100 a tyre cheaper than the KM2 i think theyre a no brainer.
Will attempt to update this thread as i test the KL71 some more. Once it bloody rains here i will test both in the same mud as well.