WPF SDK was deprecated so for my application which SDK is better and what changes for new application for converting old SDK to new SDK
Hi,
You should be looking to move to superseding product ArcGIS Runtime SDK for .NET (first released Fall 2014). We're currently working on the next major release named "Quartz" - if you're only switching now then I advise starting right away with the beta: ArcGIS Runtime SDK for .Net | ArcGIS for Developers
Cheers
Mike