For serious travel photography, would you rather use an xe-1/xpro1 or a canon or nikon full frame?

Absolutely valid, and was considered and solved.

Both. Working out of a vehicle, my D700 and heavy zoom lenses are not a problem. Since I am primarily doing environmental shots with them, stealth is not a factor. It has a GPS, which embeds locations in the EXIF metadata, which is invaluable for identifying a location in an unfamiliar place. With the 50mm, 14-24mm and 28-300mm, no matter what I find around the bend, I can react and capture.

On foot, as an urban, walkin'-'round, shootin'-stuff cameras, the X100 and X-Pro1 are ideal. Going for dinner in the evening, the X100 is in my pocket. Ultimate stealth. With an f/2.0 lens and ISO3200-6400, I can shoot in total silence, neither attracting attention, nor offending anyone. Shooting available darkness in any restaurant is a breeze, since the EVF gives a greatly brightened view. As an added bonus, when shooting outdoors in the harshest sunlight, I can shoot syncro-sunlight fill-flash better than any other camera I have ever encountered. With the flash so close to the optical axis, the secondary shadow is all but invisible. It maintains the beauty and realism of ambient light, but with wonderful levels of shadow detail.
In town and on the street, the X-Pro1 kit is featherweight. The D700 body alone is 995g, while the XP1 with all three lenses is only 967g. The camera and lenses reflect the classic photojournalists kit, which also reflects the way I work with it. Both Fuji cameras can shoot great stitched-in-camera panoramas, with the XP1 having the advantages of still being able to cover 120° and 180° on the x-axis, but expanding or compressing perspective on the z-axis. Shooting with the camera in landscape or portrait position gives me cropping control on the y-axis. I still do stitching in software, but when with a group of friends, I do not try their patience by shooting the number of exposures needed for stitching. I also have the option of video, though rarely use it.

All three can produce images of very fine quality.

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larry!
http://www.larry-bolch.com/