Personally I prefer jQuery for the following reasons:-
- The plug-in community is far more varied and attracts developers from a broad range of backgrounds (not just the MS stack). For MS-AJAX you’re pretty much constrained to the clientside AJAX control toolkit for your UI widgets at the moment.
- I find the jQuery API far more applicable common clientside tasks than that offered by MS AJAX
- Given the lack of WebForms smoke and mirrors going on in MVC you sometimes need a firm control over the DOM to do certain things, the CSS selector engine offered by jQuery really helps you do this.
In terms of what MS AJAX offers you in MVC, it can do a lot for you in terms of giving you a quick way to “AJAXify” forms and links, but as far as I’m concerned adding 90kb worth of javascript to do that isn’t really worth it when the equivalent calls in jQuery (e.g $.get, $.post, $(element).load) are relatively easy to use.