If you really want to use SPA, perhaps the Kendo tools will be a better choice: http://docs.telerik.com/kendo-ui/getting-started/framework/spa/overview.
With the client-side Kendo widgets it is easier to fetch simple HTML or data via AJAX and still use them, but the ASP.NET AJAX tools cannot be created entirely on the client because are built around the WebForms and MS AJAX paradigms and rely on the ASP.NET WebForm server lifecycle, postbacks and partial postbacks. They work heavily with server events.
A lot of the controls in the AJAX suite offer client-side data binding and all of the have rich sets of client-side events where you can plug your logic, though. In any case, you would need to prepare the needed services to fetch the data and/or use the ClientDataSource control we offer (which is, essentially, the Kendo DataSource widget with server markup).
If, however, you intend to use the controls client-side and use windows to load other pages, I cannot say which suite would be more useful and I would advise examining the demos we have for each of them to see which feature set better fits your needs. The AJAX suite may offer some more feature and controls because it is more mature, but on the other hand Kendo are a more recent creation and are optimized for HTML5 and newer browsers. If you need your app to work on older browsers, however, the AJAX tools may offer better compatibility.
I hope this helps you make the right choice based on your project's needs, requirements and limitations.
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