The stringent equality operator (===) works exactly like the abstract equality operator (==), with the exception that no type conversion is performed, and the types must be the same to be regarded equal.
Javascript Tutorial on Comparison Operators
After performing any required type transformations, the == operator will check for equality.
Because the === operator does not perform the conversion, it will simply return false if two values are not of the same type.
Both are equally fast.
"abc" == new String("abc") // true
"abc" === new String("abc") // false