I’m not a native speaker, and my teacher taught me to use "the biggest number of . . ." when comparing amounts of some things, but I’ve checked it
in googlewhich seems like "the largest, the greatest, the highest, and even the most number of. . ." are actually used more often.
1. Which do we usually use for comparing numbers or amounts of some things?
Let’s say, if there were 3 cities.
- 1,000 people live in city A.
- 2,000 people live in city B.
- 3,000 people live in city C.
2. How do you compare those numbers of people?
Teachers who are not native are often unfamiliar with many such aspects, but this is OK as they are only there to get you to a level where you can make your own decisions, and to pass exams.
‘Big’ is one of those great shortcut words, like ‘nice’ and get’, that have a multitude of uses we resort to when speed of communication is required. However, as you can see, in writing we often make a more precise choice or attempt to avoid repeating the same word, etc.
So all your choices could be used, which one depends on your preferences and the needs of your current text.