A lot of guys who attend our Bronco events (Fawl Crawl and the Roundup) run both of these. One is Brian Keeler who's my right hand man in the club. He had 35 SSR's for the last several years before swapping to 37" MTR's a year or so ago.
Brian's SSR's did a fine job on clean redrock during our trip to Moab a couple years ago and work well in mud and dirt covered rock since they are more self cleaning. The MTR's handle better on the road and are good on clean rocks, but if you have some mud on the approach, you'll be screwed. This is often the case at places like Tellico where we have the Fawl Crawl.
Another participant at last year's Crawl was Lee Novikoff from Texas who had 40 MTR's on his super trick Bronco rockcrawler. That rig is amazing but could not get up on the face of slickrock after it was greased up from those ahead of him. He spent more than 20 minutes giving it his best, but the tires just wolud not hook up. He said he really wished he had brought his Swamper SX's instead.
Seeing that you're from eastern TN, I assume Tellico is one of the places you will wheel, and that other places you do are also likely fairly similar. Because of that, I'd reccomend the SSR, however, don't overlook the BFG Krawler, IMO, it is probably has the best features from both.
The aggresive sidebiters of the Swamper designs are great at Tellico for hooking up on exposed roots and the steep cut banks like on trail 8 and 11.
I currently have 38.5 SX's, but will probably look at the Krawlers in the future.
Milage ?:? , both of us use are rigs almost exclusivly for rockcrawling with very little daily road miles. I would not expect much over 25-30K of useful tread, but I really don't know.
