Have to agree to use Stored Procedures if possible.

In my opinion, Maintainability is not necessarily an advantage of Stored procedures. You might / will be distributing 'Business Logic' over two tiers, which should be avoided, if possible.

But the gain in performance and limitation of network traffic is an obvious advantage.

It is also easier to 'hide' database implementation when using procedures.

VERY BIG DISADVANTAGE :

Code portability. Don't count on(don't think about, that is) porting your application to different databases. Just think about the differences in SP syntax between Oracle and SQL server, and then we're not even talking about mySQL (no stored procedures), Access (no support for SQL-syntax either), and so on ...