Regarding what I shoot in that range when traveling, it would be cityscapes/architecture, gardens, monuments and such outdoors, plus historic buildings and museums/aquariums indoors (when allowed). I'd also use the 6d for crowd shots and step in closer for some detail on individuals when I shoot events for local non-profits (my only semi-pro activity).
To be honest, you could use both. I really like my 35/1.4 (Canon L bought a couple of years ago, today I would quite possibly get the Sigma) as a nighttime walkaround lens. For architecture, 35mm often isn't wide enough (although the barrel distortion of the 24-105 is a problem for architecture). The IS on the 24-105 is good in museums - you get the f/1.4 shutter speed without the f/1.4 thin DoF.