So I've been thinking more about this and think the WR is the way to go. Here's why:
You don't know what roads you're going to ride. It'll be a lot easier to extract a 250 pound bike from the bottom of a snotty hill than a 500 pound bike.
If the bike breaks down it'll be a lot easier to throw the WR in the back of a truck/cart/tie it to the roof of a car than the 990.
You'll have to ship it at some point. If I remember what Aurel said correctly, shipping is based upon size and on weight. It'll be a lot cheaper to ship the WR.
Fuel mileage will likely be better with the WR. My 990 is getting about 40 mpg when I'm just cruising around 4K rpm. I would imagine the WR would get better than that and every dollar saved will help.