The IN operator is used to check if a value exists within a set of values returned by the subquery. It’s more appropriate when you need to return values from the outer query that match values returned by the subquery.

The EXISTS operator is used to check if at least one row is returned by the subquery. It’s more appropriate when you only care about whether or not the condition is met, not the actual values returned.

In general, EXISTS is faster than IN when checking for the existence of rows because EXISTS stops searching as soon as it finds the first matching row, while IN continues to retrieve and compare all values.

So, the preferred operator between IN and EXISTS depends on the requirement of the query and whether you need to return specific values or just check if a condition is met.