Dictionary and list has different structure to store the values. List can have duplicate values and it for search using liner algorithm. Hence it is slow. But Dictionary is searching on Key basis so it fast to get the values. If you have unique keys for your objects, use Dictionary. One point I would like to highlight with Dictionary, it is not supporting serialization straight forward, as it is implementing IDictionary interface. You have to write custom logic to do that.

Both are altogether a different structure. If you are looking for key,value pair then you need dictionary, else list is good to go. If question is with respect to performance, then searching is faster in dictionary

List can have duplicate values and it for search using liner algorithm. Hence it is slow. But Dictionary is searching on Key basis so it fast to get the values. If you have unique keys for your objects, use Dictionary.It is more efficient to use dictionaries for the lookup of elements as it is faster than a list and takes less time to traverse.

It is advisable to use list as dictionary objects cannot be serialized.