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

For travel the fuji's hands down. Size and weight tend to deter while small, light and convenient makes the effort a non-effort. 
The game has changed since we now have high quality,  high ISO, small cameras that do not attract attention everywhere we go. My first test of my XE1 was walking around New York City for Six hours with camera around my neck and never felt it, i couldn't say that with my nikon. For tripod work or shot trips it doesn't nmatter either way. A 35mm and 50mm 1.4 takes care of shallow DOF concerns.