When to use
Object for records where you have a fixed and finite number of properties/fields known at author time, such as a config object or anything that is for one-time use in general.
Map for dictionaries or hash maps where you have a variable number of entries, with frequent updates, whose keys might not be known at author time, such as an event emitter.
According to benchmarks, unless the keys are strings of small integers,
Map is indeed more performant than
Object on insertion, deletion and iteration speed, and it consumes less memory than an
Object of the same size.