The ASP.NET AJAX controls on the other hand are build as the native ASP.NET server controls, with all the Visual Studio integration, in correspondence with the ASP.NET Page lifecycle, leveraging all the good things of the MS AJAX Framework, providing rich client-side capabilities, etc.
We understand that now it might be hard to choose what to use. This basically should be an architecture decision based on the target users of your application and the goals of it. If the idea for everything working on the client fits your needs, you can try Kendo. If you still prefer the server-side approach, you should continue with ASP.NET AJAX components.
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed