Heresay (but 1st person heresay from a couple of top CalRoc guys) ... I've heard pretty good things about them in the mud and dirt. All things being equal, based on what I've seen at the comps, the Krawler IS a better rock tire ... especially the red label ones that Dave mentioned. I'd like to throw a set on my project, but its hard to justify that cost when the MTR is so good (based off my own experience).
And, we're talking recreational rigs here. A MTR is the best tire most of us would ever need. I've only ever heard of one sidewall ripping out (my own)
... And, I've run a set of 35s and a set of the 37R17s pretty ragged on rocks, dirt, mud ... not to mention the highway (good luck running a Krawler on a DD). The same can't be said for the couple of sets of BFGs i've cut up ... the last set of which I had to toss b/c after ~5 off-road trips, they'd hardly hold air because of all the holes.
All that said, one would have a hard time fitting the 35" krawler on a D90 anyhow because of the 13.5" width. There's going to be a lot more rubbing than an equivalent 35" MTR.