Hi there,
IMO Eclipse (Architect is plugin of Eclipse) is not a framework, it's an IDE. It's a tool to develop your application in (like the appbuilder, but then more sophisticated
DWP is a real framework in the sense that it is made purely to develop applications with. With using Eclips you probably still need to develop your own framework to develop applications in.
For instance with dwp you can make working screens without having to code one single line. Lots of stuff you encounter when developing software are already being taken care off. Stuff like screen development is made surprisingly easy. Transaction management, session management is done for you and there are standard reports available for every screen (pdf, excel). It also supports different UI's (.NET, WebClient, Ajax, etc...).
In Eclipse no such functionality is available. So if your choice depends those 2 choises then DWP would be (by far) the best choice of those 2.
Saying that, choosing a framework most times depends on more issues then the ones you stated. And only by gathering all the requirements you have for a (new) framework you can come to an answer.
Regards,
Casper.