P.S. That KX500 (and its rider) at 1:37 is a total beast!
I think they probably could with the right rider and suitable gearing. It surely would not be easy though! The reason I think they probably could is because you can get a pretty good run at these and victory is all about sheer speed up to about the 80 percent mark, then some careful throttle and clutch modulation to get up over the last stretch. It would be interesting to find out
Assuming they could get to the top, which of these two models would it be easier on (assuming relative equality in suspension performance and tires)? I'm inclined to give a small edge to the WRR due to weight and chassis superiority. Finally, would these hills be doable in second gear, or do you need third (depending on the bike, I guess...)? That's something I don't have a lot of experience with, having owned mostly small bikes which can't get out of their own ways in second gear. To put that question differently, how fast would you need to be able to top out at in order to have enough momentum to get it done? 36 mph? 40? 50? I'd make an educated guess that 40 mph would be sufficient. More than 40 or 45 would rule out the stock-motor WRR.
Can't help but wonder about things like this since I might (will, hopefully) have one of those one day in the not-too-horribly-distant future...