not exactly sure what you're asking but if lower rolling resistance and occasional dirt use is a priority why not the Extreme? According to Schwalbes info they have better grip in all conditions and better rolling, all you get with the XR is longer wear. I've been riding with a variety of tires on my LHT around town and with loaded groceries using an XR on the rear and Supreme on the front along with other tires. For loaded riding I think it's kind of irrelevant(unless using thick liners and thick tires) and the place where rolling resistance is perceived is a completely light bike.

I'm kind of soured on Schwalbes just from the cost.