A hotel chain wants its headlines to dynamically mention the specific city a user is searching for (e.g., "Hotels in Miami"). Which customizer should be used?

The hotel chain should use location insertion. It inserts a location value — city, state or country — into the ad text based on the user's location or the location they are searching for, so one ad can render as 'Hotels in Miami' for one person and 'Hotels in Chicago' for another. That removes the need to build separate ad groups and hand-written ads for every city, which for a national chain would mean hundreds of near-identical ads to maintain. Location insertion needs a sensible fallback in case no location can be determined, so the ad still reads correctly, and the landing page should match what the ad promises: someone who clicks 'Hotels in Miami' should land on Miami availability, not a generic homepage. Handled that way it lifts both relevance and conversion rate.