I've run Reds, Nitto stickies, 37 and 40 Treps, SXs and now currently 42 Treps. My rig is a 4500# somewhat technical crawler. For my rig, without a doubt the Treps work best by far.
Just this last weekend, i literally crawled up a ledge at The Flats that my SXs never allowed me to cllimb...