While I can understand and agree with much of the logic and sentiments, I can somewhat argue the quote of "(twice the duner the XR650R ever was--".
It depends on what you want to do in the dunes. If carving and slicing a dune is your thing, the CR with be much better of course. But if you want to go balls to the wall over extended heavy sand whoops such as between Glamis's Sand Highway and Competition Hill, the XR650R with smoke through sections like that with properly setup suspension for the rider. Or, try the long chopped out section along the west side of Gecko Road. The XR650R will kill the CR. When you want to cover serious ground across the dunes, the XR650R is a machine to be reckoned with.
You can ride sideways just below the crests of the steepest dunes such as at Dumont for extended lengths without a problem. I will give quads fits by doing this.
The added benefit is you don't have to be full on the gas or in the powerband to be doing this kind of stuff on the Xr650R.
With all this said, I myself have considered an older CR250 for an alternate, (green sticker) bike for some riding conditions such as tight, technical woods riding and other possible uses, (such as an alternate dune bike for *dune carving*) for a change of pace and options. There is no doubt a CR250 is fun and exciting for carving lines in the side of dunes. The 650 will smoke over & across them like nobody's business. I have ridden with 250s, 450s and 500s and their is no denying that the 650 stands tall in the dunes. .
I don't disagree with any of that. The XRR does excel in the areas you mentioned. I can specifically remember riding the XRR in some areas at the ISDRA and thinking to myself, "this bike was made for this."
But those aren't my favorite places to dune ride. Mostly I'll only find myself in the places the XRR really likes when I'm just trying to get from point A to point B. When I'm just going out with no particular distination you won't find me pounding out miles of whoops. I guess I should have said that the CR is twice the duner for me. I've found the XRR is just too heavy and I could never get the front end to feel planted (like the CR feels) when carving. For my dune riding, the XRR has a higher "work-quotient" while the CR has a higher "fun-quotient", if that makes any sense. Like I mentioned I've had both bikes out there at the same time and never chose to ride the XRR.
I think we're pretty much on the same page--just getting down to the nitty-gritty so nothing gets shortchanged.