Bronica RF645 w/ 45mm lens would be my choice. . . .obviously. Surely I'm getting to be too much for those that encounter my pervasive adoration of that Bronica beauty. I have not owned the Fuji.
The CV 15mm is a beautiful lens, but vignettes heavily, and is not very sharp because of its physics. I mean, it's sharp, but not sharp enough to make strong enlargements from 35mm negs if you're shooting landscapes where detail is important. You'll have to meter for a center filter as well. .. could be a pain.
It is very VERY true that you'll come to feel that wider lenses, especially the superwides, are not the best for landscape photography. As much as they seem a good idea, they tend to push things too far out. You'll end up cropping lots of the frame out when you print. Unless you are shooting a subject that really fills hte frame, like a mountain range close up or a tree.
Here is a landscape with a 75mm lens on a Pentax 645NII :
http://www.shutterflower.com/landscapes gallery/pages/gateway-to-heavenRFF.htm
That image brings the subject, the real power of the image, front and center. It is wide enough, but doesn't push things back. Nice balance with the sky.
Superwides work in instances where you'll be standing in a field of flowers or in the city. You would find use for a superwide where you are standing IN the subject. Field of flowers. . .in a bus. . . . in a waterfall. Here is an example of when a wide lens is nice :
http://www.shutterflower.com/street scenes gallery/pages/private-gardenRFF.htm
There you have need of a wide lens because you have use for the foreground.
Two options, both of which require the Bronica :
I'd bring the Bronica with the 45mm because then you'll have a very wide (like 24mm) lens that is super sharp (biogon) and controls distortion very well. You can then crop 35mm sizes shots from those negs that will have 50mm zoom on the subject if needed. See my website, in the street photography section, for examples of the 45mm. Most all of the images in that gallery are with the 45mm.
OR
I'd just buy the 65mm lens (kit from KEH) because 65mm is wide as well. Big thing with the 45mm is that you can crop panoramics from the frame if you shoot horizontally. 65mm has shallower DOF, which means you'll have to shoot at a smaller aperture. . . could be an issue.
And finally, the Fuji 645 series. They have sharp, simple lenses. They are not as well built - not even close - as the Bronica, and they don't have interchangeable lenses. I have almost never been please with autofocus cameras when shooting landscapes, so stay away from the AF Fujis. You're only real reason to buy the Fuji is that it is about half the cost of the Bronica (and the Bronica is about 1/3 the cost of the Mamiya 7).