WPF or Windows Forms ?
_Windows Presentation Foundation (WPF) is a next-generation presentation system for building Windows client applications with visually stunning user experiences. WPF supports UI, media, documents, hardware acceleration, vector graphics, scalability to different form factors, integration with Windows, interactive data visualization, and superior content readability. Read all about recent updated and additions to WPF here.
Windows Forms is a set of classes in the .NET Framework that enables rapid development of rich Windows client applications, with powerful, extensible libraries for user-interface controls and graphics.
You can incorporate WPF in your Windows Forms applications through WPF-Windows Forms interoperability in the .NET 4 Framework.
-- From Microsoft_
You might heard about that Microsoft never said WPF is the future and Windows Forms will be washed out.
So, if you don't know how Microsoft will do, just watch their official site: windowsclient.net, and check the home page at "Articles of the Day" section, how many articles are about WPF or Silverlight ? how many articles are about Windows Forms ?
Let me say: Obviously, WPF should be the future, Microsoft might no more spend too much cost and time on the new stuff for Windows Forms , they might combine all features of Windows Forms to WPF.
Windows Forms is legacy. Microsoft should label Windows Forms as legacy (as it has done with COM), only offer bug fixes and concentrate 100% on WPF. WPF is the future. I’ve had more fun building WPF UI than I’ve ever had with Windows Forms. -- From mdavey.wordpress.com
Also, here is another article about WPF vs Windows Forms