What is the difference between streaming portal(desktop) and file based portal?

I have come across this question many times while working at client site from co-workers, clients and infrastructure folks - what is the difference between streaming portal and file based portal? Well, during portal development process we create .portal file in workshop. This is basically just a template in which more books, pages, portlets can be added. The .portal file is XML based and rendered as "single file mode". This file is mainly for development purpose and should not be used in the production though you can access it in production as well. You can not apply any entitlements or user customization as no data base involved in .portal template.

The streaming portal(desktop) is created out of .portal template using weblogic portal admin tool. A single portal template can have any number of desktops. A desktop contains all the portlets, content, shells, layouts, and look and feel elements necessary to create individual user views of a portal. For eg, assume I have a requirement from three different clients to show some functionality of a portal. I don't want to create a three .portal template though I could, but I would like to have three different desktops with similar functionality but with different "look-and-feel". So I go to weblogic portal admin tool create a desktop called sample1 for client 1. sample 2 for client 2 with different look-and-feel. sample 3 for client 3 again with different look & f. Oh yes! Look and feel can be applied at run time ie while creating desktop itself. Also I can add/remove portlets if I want to for any desktop. I can also add/remove any book/page at run time as well. So what I have done is created 3 different desktops but with a different look-and-feel per client.

When I create a desktop from a .portal template, the desktop is decoupled from the template, and modifications to the .portal file do not affect the desktop, and vice versa. For example, when you change a desktop's look and feel in the WebLogic Portal Administration Console, the change is made only to the desktop, not to the original .portal file. When you view a desktop with in a browser, the desktop is rendered in "streaming mode"  from data base.

P.S: If your portal application does not need any entitlements or personalizations and it is simple, static portal then file based portal is the best choice. File based portals give better peformance and propagation to other environments is also easy.