I am not very good with IAS but just by looking at your post, one thing I can say is "SCALABILITY".

When you have everything in your database, you are limited on scalability and load balancing the load on application components.

Using a middle tier server, you can separate the logic, data and the presentation into individual components.

If scalability and number of users is not an issue then using the database may solve most of your problems.

dba