I've run those KM2s on my JK for just under a year now and I saw little change in ride quality (smoothness) over the stock 225/75-16 Goodyear Wrangler ST that came on the Jeep. This is particularly interesting considering Baton Rouge's roads suck. I can run all day on the roads down here and the noise level is also just slightly higher than the STs were. These are some quiet MTs and they do well in the rain so far. Had many a person in the Jeep with the top down who commented on that. A favorite was a friend who said "I thought you had mud tires, where's the roar?"
I run them at 35 to 38 PSI at the moment, so they're a bit stiffer than when I first put them on at 30PSI, but nothing terrible. I seriously doubt you'll feel much difference between a D and E anyways.
• 2010 Jeep Wrangler Sport (JK), 6spd, 3.73, 3x12.50-17 BFG KM2s on 17x9 ProComp 7069s, Flat Flares, Stock Suspension, Shrockworks Stubby Winch Bumper w/Milemarker HI9000 & Viking line, Cobra 18 w/Firestick II, Clarion & Boston Acoustic Audio