The iroks actually did very well in the early spring snow. I've never seen an SX (or any other modern tire) in this situation so I have nothing to compare to.
The Iroks also do ok in mud. I saw a set of SX's clearing out much better on the Eagles nest than a set of Iroks one muddy day (at crawl speed), however, my 39.5" must have had something to do with helping me take 3rd in the open class at the King Challenge (very muddy logs, mud pit, tire pit, gauntlet). I also did some pretty good early spring mountain trail mud, but once again, no other vehicle/tire to compare with on these runs.
On Rock, I do believe the Iroks hold me back … a lot.
I’ll still wheel with a certain local Hillbilly even though he gives me continual crap about my Iroks.