I\'m working on an application we made WPF instead of Silverlight as we wanted a full blown desktop application with the whole unique feeling and advantages that gives. Howe
If your reasoning for WPF is that you want a full blown desktop app, then silverlight is not an option. If instead you are interested in a web-based app that can leave the browser, then Silverlight 4 might be what you're looking for.
From the wording in your question, it sounds like you want the full desktop experience, so Silverlight is irrelevant.