Silverlight Out of Browser technology and WPF ClickOnce on the surface have similarities. Easy and simple deployment, the ability to specify the level of trust access to the
Given that you are targetting a private infrastructure running Windows, two points worth thinking about
While your target platform will likely have the latest .Net framework installed, rendering this last point moot, keep in mind any updates to the framework [ie .Net4.0 and any future updates] may require a restart of the machine - which is a major pain point for businesses that demand constant-on stateful desktops [ie anything in finance, like banks and trading].
As with all problems, your requirements, not the technology, should inform your solution. :)