Writing queries in Drupal 7

Drupal 7 provides a way to simplify your database queries by using the DB:TNG API. But you can also use db_query to write a query. For example, here are two queries which do exactly the same thing.

But which one is better? As always, the answer is: it depends. Read a more satisfying answer at stackexchange. There is also an issue at drupal.org to compare the performance of the two functions.