Definitely easier to maintain if you put it in a stored procedure. If there's difficult logic involved that will potentially change in the future it is definitely a good idea to put it in the database when you have multiple clients connecting. For example I'm working on an application right now that has an end user web interface and an administrative desktop application, both of which share a database (obviously) and I'm trying to keep as much logic on the database as possible. This is a perfect example of the DRY principle.
