A city break built around walking directions and messaging needs a different allowance from a work trip with video calls. Light users can often manage with maps, messages and occasional browsing, while frequent social video, cloud backups and streaming can use data quickly. Think about your normal routine rather than choosing a plan by trip length alone.
There are easy ways to stretch an allowance. Turn off automatic photo backups until you are on Wi-Fi, set app updates to Wi-Fi only and download music, podcasts and shows before travelling. Most phones also show which apps have used the most data, so checking those settings before the trip gives you a realistic starting point.
If your plans may change, flexibility matters. A little extra data can be useful for a delayed connection or an unexpected day trip, while a shorter plan may be enough for a quick stopover. The best choice is the one that matches the itinerary and leaves you comfortable using your phone when you need it.