There are two types of equality checks that you can use with Immutable.js collections: strict equality and deep equality. Strict equality is cheaper and therefore it is faster than deep equality. On the other hand, there are some things that deep equality can do that strict equality cannot.
In JavaScript, the strict equality operator compares the memory address of values, not the actual values. Immutable.js collections can't be changed, which means that the strict equality operator doesn't make much sense to use with Immutable.js collections. There's one important use case where this operator does make sense to use with Immutable.js collections—change detection.