The benefits of SOA based component applications has been widely discussed. Having built these applications using reusable web-services, the next iteration is presenting this functionality via a user-friendly front end.
There are two choices to this from an Oracle perspective. A portal based front end, or an OBIEE based dashboard that presents a graphical version of the raw data. It could also be a combination of both.
In either case an SOA implementation requires a presentation layer to provide a UI to the functionality and integration that has been created. The right choice of front end is crucial to end user acceptance. BI based dashboards, where applicable, are the most intuitive for end users. Portal functionality is useful when multiple data sources are being brought together.
With Web 2.0 functionality providing yet another choice, this area of discussion will continue to be an area of healthy debate