There is always more than one way to do one thing in any programming languages. In SQL Server there is always more than one way to achieve same result set. It is quite often I see that developers write subqueries in place of joins or joins in place subqueries.
First of all answer this question : Which method of T-SQL is better for performance LEFT JOIN or NOT IN when writing a query? The answer is: It depends! It all depends on what kind of data is and what kind query it is etc. In that case just for fun guess one option LEFT JOIN or NOT IN. If you need to refer the query which demonstrates the mentioned clauses, review following two queries for Join Better Performance.