My first zoom lens, other than the 18-55mm kit zoom, was an 18-200mm Tamron, based on my wife really liking her agency's Nikon-fit Tamron 18-200. When I later bought my first 7D, which was packaged with an EF 28-135mm IS, I found that the Canon hunted (for focus) less in low light, and with less zoom range, had less distortion at each end of the range. Of the two, the Canon 28-135 would certainly be my preference for walking about in a city.
I later acquired the excellent 10-22mm EF-S, which complements the 28-135mm very well. If I did not want to swap lenses in the open air, I could be happy with either one, though, of course, the 10-22mm zooms from ultra-wide- to wide-angle. whether this is a handicap, or not, depends upon the environment, and one's plans for the day. Some cities are more densely constructed and vegetated than others.
One lens that I briefly used, while evaluating a camera for purchase at a large photography dealer, was an 18-135mm EF-S. I was quite impressed by its focusing ability and images, and wished I could have afforded to buy it along with the camera. Sometimes, indoors, my 28-135mm is not quite wide enough.
I have only mentioned specific budget zooms, because that is the limit of my actual zoom lens experience. I am acquainted with local event photographers who really like their 24-70mm 2.8 EF lenses, as working lenses on their full-frame pro Canons. I am not sure what they would choose as a travel lens.
Canon 7D/5D/40D/1D2N; Nikon F6, D700, FM3A, & Coolpix A; Canon 40mm 2.8 STM, 135L, 50L, 35L, 50mm 1.8 I, 100mm 2.8L Macro, 10-22mm EF-S, 28-135 EF, 400mm 5.6L; Nikkor 50mm 1.2 AI-S, 50mm 1.4G, 50mm 1.8D, 16mm 2.8D Fisheye, 180mm 2.8D, 100-300mm 5.6 AI-S, 18mm 2.8D, Voigtlander 90mm f/3.5 SL II