Deep, the factors that should help you determine which product to use is your application concept and foundation. This is what I wanted to stress on with the information and resources referenced so far.
In case you will be using a certain server framework like ASP.NET AJAX or ASP.NET MVC, the corresponding products of ours - RadControls for ASP.NET AJAX or Telerik MVC Extensions - might be the more appropriate option for you. They take advantage of the server functionality exposed by the respective framework, incorporate HTML5 features and client APIs, and help you create and initialize the controls on the server. Again, you can use web services to communicate with the server and perform some operations. Both suites are touch-friendly and thus you app will be usable on mobile.
Hope this additional explanation helps. The final choice what technology you will use depends entirely on you, though.
the Telerik team
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI