Have had both bikes--both new--rode the TAT on the WRR, Sold it--when KTM and Husky. The WRR makes the power way up in the rev band, when geared for the mountains it suffers on the flats trying to reach 80mph. It ate one swing arm protector around OK (I rode Myrtle Beach to TAT to Oregon) second swing arm protector was done in by OR. I spent the entire trip wringing out the WRR. I would not do it without the bigger tank and then I carried extra fuel on some legs of the route.
In my experience in the mountains the stock CV carb will perform as well as FI--all of my normal riding is above 6k and up to 10-11K.
My RR is around somewhere (http://www.advrider.com/forums/showthread.php?t=710618
) and the WRR did a great job for what it is--a 250cc. Look in the RR's and I can think of at least 2 others who did the TAT on WRR's. On resale mine got hard to move with over 10K on the clock--traded it on the 510 Husky.
I was riding solo and traveling light, I also lowered the WRR, it was easier to pickup and since I was riding solo I went with it.
If I were doing the TAT again it would not be on a WRR, unless my only choice is a DR650, which is just too heavy for me to deal with if I were to go down in sand with especially with a tail load. So to answer your question WRR or DR650--I would again take the WRR.