
Corbin P. answered 08/22/20
4th Year Computer Engineering Student
The biggest difference between map and unordered_map is the ordering - if you need the keys to be in order, then definitely don't use unordered_map.
If that is not a requirement, then your best bet would be to use unordered_map because of the fast lookup runtime as you mentioned. I too have heard that small numbers of data may allow a standard map to perform better, but since you restricted the question to > 1024 keys then I don't see any advantages of map over unordered_map.