JQuery also has package to make nice User Interface by using JQuery UI. JQuery UI has many themes that makes it more flexible and usable by developer.
Asp .Net Ajax Toolkit and ScriptManager
Asp .Net has its own Ajax Controls. There are main components of Asp .Net Ajax controls which are ScriptManager, UpdatePanel, and Triggers. ScriptManager is a must have controls to enable Ajax.
Those controls are server control by attribute runat=”server”. So that Ajax submission will be done with .Net powerfull script and also VS intellisense. Server side script in Asp .Net is easy to manage. Has relatively less lines of code than any technology by help of so many .Net references that available. OOp implements automatically so that developer can make their best practice on OOP design.
Those reasons make general and Ajax Server side script on Asp .Net leads on easiness and fast for application development.