I put my 255/80R17 KM2 LRE's back on last week for fall hunting. I then did about 600 miles this weekend, 265 of which where at 21K GCW.
The LRG's handle the weight much better, and empty there isn't much difference. The LRE's are noisier, but exhibit the same characteristics of the LRG's. There is a little more road feel transmitted with LRG's, but not much.
They each have their purpose, I need the ability to air down the LRE's for fall hunting and will drop to 40/25 for 10 days or so next month. That's below the air required for the weight, but speeds won't exceed 20 for several hundred miles.
I drove the same 120 mile round trip on dirt, with a trailer, this summer with the 19.5's as I did this weekend. The 19.5's just don't do as bad as people think on dirt roads. They aren't crawling or mudding tires, but 99% of the time they operate the same.