For my recent trip to TW, was quite satisfied with just a 12-35. Was a regular chillax/sightseeing trip with friends. Don't think I would have had time to bother with changing lenses, or even decide in a split second which lens to use. That's one factor taken out of the equation, so I could just focus on framing/subject. How it usually works for me when I travel with friends: Walk > see something interesting > stop briefly > CLICK! > Walk quickly (or run, depending on how long I waited for the 'moment') to catch up with friends > REPEAT ;p