Final answer:
Dictionaries and sets in Python are similar in that both can be created using curly brackets {}. They differ in functionality; dictionaries are key-value pairs, and sets are unique element collections.
Step-by-step explanation:
Dictionaries and sets have one key aspect in common that distinguishes them from other data structures both can be created using curly brackets { }. A dictionary is a collection of key-value pairs where each key is unique, while a set is a collection of unique elements. Both dictionaries and sets are implemented using hash tables, which is why they share the trait of being created with curly brackets. However, dictionaries associate values with unique keys and can be accessed using these keys, whereas sets only contain keys with no associated values.
Contrary to the other options provided, neither dictionaries nor sets are immutable; both can have elements added or removed. Also, sets are not indexed by integer values whereas dictionaries can be said to be 'indexed' by keys, but these keys can be of various data types, not just integers. Moreover, dictionaries in Python 3.7+ and sets are considered to be unordered collections, but it's important to note that as of Python 3.7, dictionaries preserve the insertion order due to an implementation detail that became a language feature, while sets still do not guarantee any order.